CD sucks ass, my good man. It's a terrible, jumbled mess of a game, with a few good ideas here and there. The GG games were, in fact, pretty darn good (and way superior to Sonic CD). Well, except for Sonic Blast.
If you played the GameGear games on their intended platform - the Master System - they were amazing. Not quite MegaDrive Sonic tier, but extremely good. Sonic 2 and Master System is one of my favourite Sonic games.
I don't agree, but that's a moot point anyway. Most modern Sonic games are "pretty terrible" compared to the classics, but Sega's still including levels from them. Besides, it's not like they're just going to copy n paste the gameplay/level design from those games anyway.