which language seems the best to learn?

As catalan and basque are not very usefull, unless you live there, you have to meaning choices : Portuguese and French.

As they are classed respectively 6th and 13th in the ranking by total speakers you can deduce yourself which language you must learn.

I agree with Francis.
Should you live in the US after you graduated, then
I'd opt for Portuguese, as there are far more people
in the US speaking portuguese than french.

French has fewer native speakers than Portuguese does worldwide, but in terms of international relevance French is (still) more important: for example, to communicate with Eastern European countries (namely Romania, Czech Republic) Frenck is often a better choice than English, especially if your speaking with older, educated people.

On the other hand, speaking Portuguese may be an advantage when it comes to het a job related with Brazil. And the importance of French is dimming.

Also, if your major is Spanish (Castilian), learning Portuguese would be much easier, as the two languages are quite similar. Beware, however, of many false friends (e.g. "presunto", which in Castilian means "assumed" and in Portuguese means "ham").

Curious thing: most Portuguese understand Spanish, while most Spaniards have a hard time to understand Portuguese. (That is not only due to their lack of interest, but also because the Portuguese phonetic system is much wider than the Spanish.)

Hm, I would have thought that people from the eastern
european nations spoke russian as a second language,
and neither english or french. At least that's what I
have experienced in dealing with people from these
countries.

Yes, that would be the case for people of Slavic language, specially if their country borders with former USSR. But Rumanian is a Romance language (the name itself states that) and their cultural relations in the XX century (and maybe sooner?) were always with France. Many Rumanian intelectuals got refuge in France when the Communists took over.

As for the Czech, their language is Slavic, but they're quite distant from Russia, unlike the Poles they were never under Russian influence (except during de Warsow Pact period) and being mostly Catholics meant that there was a number of factors opposing mutual relations. German was quite important in Czechslovakia, but there was a split feeling towards the language: the relations between the Czech and the Germand and Austrian were often less than peaceful. (BTW, the Communist period had an interesting side effect: the Czech put their time under the Austrian Empire under a new, brighter light...)
But why was French an important language among Czech intelectuals? Basically, because it was a language of prestige. That happened a lot all over Europe. In the XIX century nobles and intelectuals in Slavic countries wrote their personal letters in French -- even if they were writing to other Slavic-speaking person. It was 'chic'. That happened also in other countries, like Portugal. I guess that reverence (sp?) towards French perdured in some Eastern European countries for a longer period...

But remember: I'm talking about the few literate people, not the common people; problably Rumanian peasants would speak some Russian if they lived near the border.

It is hard to imagine that those "intellectuals" from XIX century are still alive. It was really used to write letters in French that time among the elite, but 95% of population was very far from that group of people, thus unlikely it was widespread language

If you want to learn to translate a spoken language, I'd go with Portuguese. To my ear, it's one of the most beautiful languages on earth--a nice bonus! If you plan to explore a literature as well as the spoken word, I'd still go with French--although its prominence is fading, its lit is extensive and powerful. There is no Portuguese analogue, of quality, to Voltaire, Proust, Camus. However, there are very good Portuguese novelists, poets, and songwriters. I enjoy Portuguese more than French, but French lit and science (if that's an interest of yours) have the depth.

BTW, If you speak several languages, as I do, you'll get some joy in life!

I'd like to learn Italian, I like this country and I like South and sea. Though Italian culture absolutely is not similar with my own, there is in it something very attractive for me.

French Sucks, learn Portuguese
I speak Spanish, Portuguese, Italian and French. I can tell you from experience that you are more likely to use all of them in the abovementioned order in the USA.

Spanish (obviously)
Portuguese (I use it all the time in my business with Latin America)
Italian (in Italian restaurants)
French (I never use it)

Everyone needs to know Spanish if they want stuff done in the USA.
There are thousands of Portuguese speakers where I live (NJ) and the girls are freakin HOTTIES!
Italian and French are really useless unless youa re doing business in those countries. I am being honest. Don't bother learning them.
Catalan, Galego, Basque may be fun to learn, but they are useless outside of Spain.

I know I am gonna get flamed by the world's Italian and French speakers, but it is the truth, in my VAST international experience.

Take the challenge and learn Chinese. That is the way to go in 10 years.

Well, portuguese is my native language and I must say I'm amazed with your compliment, as I find portuguese not very nice to the ear - at least compared, let's say, to italian!
Now, I also had to tell you something about what you said about the inexistence of portuguese writers as good as Voltaire, Proust or Camus... I do not agree and trust me I'm not saying this to defend this country because I am no patriot (born in an ex-colony, Mozambique, how could I be?). We do have amazing works but since we did not have conquerers like Napoleon, who was in fact responsable for the expansion of french language in Europe and even Russia, we didn't get to show off our writting.
I find Camoes, Eça de Queiros and the recent Antonio Lobo Antunes (every year he's a candidate for the Nobel Prize) all bright like the best in every other language authors. You can find translations of all these I mentioned in english and many other languages, just most people don't bother to get to know them, like I said because the portuguese never forced themselves in cultural ways to any conquered people.

Kya

You say so because you have an "Elephant's memory" or what?

Have you read that one? In fact it's one of my favourites'
The most recent books though aren't so good. He lost some of his original self while trying to sell more books :p
You are french, right? Eça de Queirós is our Balzac

I read that one and some others. I even read the last you cite.
Some French even read portuguese and brazilian literature.

Kya

Welcome to A2K! And thank you very much for the good reading tips. I am on my way to Amazon right now.

I cannot imagine growing up in Mozambique. I recently finished a childhood memoir that is from life on the Mozambique-Zimbabwe border. Many of the older European colonists sounded as brutal as the mid-day heat. I hope that you are well and happy now.

Ok so if you chose anything from Lobo Antunes, try to get things older than the 90's. His chronics (maybe they kept the names when translated) are great!
I didn't grow in Mozambique, but my parents did. In fact, my father was born there. But I was raised as mozambican (ok now you got me, I don't know if this is correct) and the mentality is so diferent from portuguese people! You would think I should understand them because I grew up here in Portugal, but I don't! I still find so many strange things in my everyday life I wonder if I will ever feel that I belong here. I don't think so. I keep thinking I'd rather live somewhere else and dream of going away someday. I have felt more "at home" in Brazil than here.
In second hand, I've felt all that hapenned in Mozambique through my family over the years and I carry that inside too. My grandfather died without seing "his country" again and that makes me very very sad too. He worked there for over 40 years, married and had children, was ready to retire when everything he worked for was taken away and he had to go back in time some 50 years, coming back to the home he left hoping for a better future. That is something terrible and it doesn't die on the first generations that went through that. Maybe my daughter will not feel this way, but I do. Thanks for the welcome