If you got bored of Sonic Generations before the first boss then simply you just don't like current Sonic games, regardless of quality. The general consensus is that Generations and Colours are both good if not great Sonic games. And I wouldn't change much about the series going forward. I especially love the on the fly perspective switching and I think Sonic Colours especially got the right level of platforming vs speed.
It's the same with me and GTA games, I don't doubt they're well made games or whatever, but I never find them compelling, I end up just goofing about, looking up the all weapons cheats and killing people until I'm bored.