I like G1, judging by what little I've seen of it, which consists of two movies and a couple episodes. I thought the characters were fun and the movie songs weren't bad at all. Some of it had a little bit of an edge, which was nice to see and unexpected.
It's a lot better than G3, which, to me, is such pap that I gag on almost every scene. They really needed to read some of those scripts before they okayed them for production. I know the target audience was little kids, but little kids aren't that undemanding! I appreciate the fact of G3 without particularly liking the finished product.
I haven't really seen any of G2, but I'd be curious to give it a look.