My favorite model so far is definitely the one they're using right now, both the in game one and CGI one. For my favorite modern 2d art, I'll have to say Uekawa's current art. However, I'll add another design that I love that hasn't been mentioned yet, but will probably cause raging.
Just. Freaking. This. I LOVE the Genesis design. This is what it would be like if Sonic's growth process made SENSE! Don't get me wrong, I LOVE Classic Sonic (especially Oshima's), but this is just something that makes a bit more sense for Sonic to grow up from. The green eyes, the inbetween quills, the slight pudgyness, it's all something that makes sense for Sonic to start as. Even then, it's a great design all on it's own, and think they should've made a spin off where Genesis continued, or at least a Sonic Universe arc. It would also be cool if they had this design in the games somewhere, just for fun, like a bonus mode.