Sonic Rush Adventure - It's wrought with so-called "hold right to win" but it offers enough feedback that it's fun. The story's also pretty nice and very serviceable to its predecessor. The music is really fun and dance-able, the graphics are nice and colorful. Not to mention, the vehicles are fun to use. The thing that really holds this game back, however, is the necessity to collect Material to upgrade the vehicles. This often has you repeating the same stages over and over with absolutely no variation. As such, it's probably the easiest game to get really sick of. But when playing on your own accord, it's still quite fun!
Sonic 3 & Knuckles - I feel this game is the successful middle ground between Sonic and Sonic 2. Sonic 1 had great level design, in my opinion, but being the first in the series it naturally suffered from slower movement. That's not to criticize Sonic 1. It was perfectly acceptable for its time, and I'd say from a general standpoint, it would still be a great game if it were designed today. However, as a Sonic game, we've come to expect a certain level of speed that Sonic 1 doesn't exactly offer. Sonic 2, on the other hand, is almost fast to a detriment, but I feel its level design (while fine) falls short. Sonic 3 & Knuckles, on the other hand, nails it in both regards. A great sense of speed, but with great level design that emphasizes speed as well as careful platforming. Plus, the music is downright amazing!
Sonic Lost World - Okay, I know this game is derisive and I do recognize its flaws, but I'm sorry. This game is wonderful. I never felt like the controls were betraying me, and the story is simplistically passable. (I don't really feel any Sonic game has ever had a truly spectacular plot, so I really don't have super high expectations) The music has some low points, but I feel it was overall super well composed. The art style is gorgeous and cute, and aside from being forced to collect animals, it was pretty fun all the way around. Great game. I'm kind of sad to see that the overall reception of the title means we might not get a sequel which expands upon and properly improves upon it.