Definitely Adventure. It's part of my favorite series in Sonic (Adventure series) and I just generally like it. I like the dialogue for how cheesy it is, I like the gameplay for how fast, well flowing it is (exactly how a Sonic game should be), and I like the music (especially the vocal tracks) for how catchy they are, and I especially like the graphics for how good the shading is.
But Tainy! The shading is really bad! Everything is so shiny and wei-
Sorry, I couldn't hear you over the Dreamcast version, which is a MASSIVE improvement over the "enhanced" port. Seriously, if you haven't read this, check it out. It's a comprehensive guide to every way SADX screwed up the game.
Thank god for mods which fix it all back up to the Dreamcast versions.
Posts way less than they probably should. Shigu shigu.