You have a lot to learn -- about yourself and about girls -- before you'll be ready for marriage. Take your time and learn. A lifetime is a very, very long time.
If I understand you correctly, you never actually had a dating relationship with Girl #1. You have feelings for her, but that is not love. It's infatuation. It takes a lot more than feelings to qualify as "love." Love is what you've been through with someone. It's what you have when those feelings go away (and they will, they always do, they're never permanent) and you still feel like that person is a part of you, and you can't imagine life without them. It takes a lot of time together for real love to develop. You're not anywhere close.
If you care about Girl #2 at all, you will cut her loose. You don't love her ... you don't even have strong feelings about her. All you're doing is using her, and she deserves better than that. Everyone does. So do the right thing. Tell her you think she's great but your heart isn't in it, and let her go find someone who can be what she needs.
After you've ended it with Girl #2 (not before! no cheating!), call Girl #1 and see where it goes. You've gotta try. If you don't, you'll always wonder if it could've worked, and that will ruin any other relationship you have.
You're just at the beginning of things. Take your time. There is no rush.