I think one thing to look for is TV listings. Stuff isn't going to be on the air for long unless advertisers can make some sort of a profit, which translates into network profits. Animaniacs isn't on anymore (at least, I haven't seen it in years), and it's not due to a lack of quality -- it was produced by Stephen Spielberg and all -- it was more likely due to something else being more profitable.
And profit comes both from later sales but also production costs, which come earlier in the equation. This is one of the reasons there's so much reality TV out there -- it's just very cheap, production-wise, so there's less of a push for ratings because those shows have to jump over a much lower bar in order to become profitable. They are cheaper partly because of less (but not a complete lack thereof) scripting but also because the "talent" works considerably more cheaply.
But that's just TV. There are also, as you know, comic books. There are web comics, too -- lots of delivery systems for this sort of entertainment.
So I think your Google search (and yes, you
should search for this on Google) should encompass things like Nielsen TV ratings, MPAA film profits and any objective gauges of popularity that you can think of for comic books. Just because someone's website claims that their comic is popular doesn't mean diddly. You need to get this information from an objective, independent third party and I'm sorry but I don't know who does the investigations into comic book popularity.