Here's my definative Sonic compilation disk, if you ever cared to know. *Ahem*...
---The Beef 'n' Potatoes---
Sonic the Hedgehog
Sonic the Hedgehog 2
Sonic the Hedgehog 3+K (The separate games are not necessary)
Sonic CD (With the option to toggle between JPN/PAL and American soundtracks)
Sonic Adventure
Sonic Adventure 2 Battle (With the option to transfer Chao data to your Sonic Adventure profile and back)
Sonic Heroes (For some odd reason, I've always enjoyed Heroes)
---As unlockables---
SegaSonic Arcade
Knuckles in Sonic 2
Sonic Spinball (As different as the game is, I still like it)
Blue Spheres
Knuckles Chaotix
Sonic 3D Blast (Saturn Version, please)
Sonic R (Saturn version)
Sonic Rush (Being nit-picky, but it's my favorite of the Advance/Rush series)
---Other games---
Flicky
The Phantasy Star series (I through IV)
Outrun 1 and Outrun 2
Puyo Puyo
Ristar (Genesis version, derp)
NiGHTS into Dreams (w/ Christmas features)
Burning Rangers
Chu-Chu Rocket (Dreamcast or GBA version will do)
Billy Hatcher and the Giant Egg
Jet Set Radio (Has nothing to do with Sonic, I know, but still an awesome game with an emphasis on speed)
---The Rest of the Crap---
A navigatable "Sonic World" hub with missions and stuff, using the Sonic Adventure engine
Instruction manuals for all versions of all games listed above
A comprehensive sound-test
Detailed information of all released Sonic Team/Sonic games
Profiles of all relevant people related to Sonic Team
The full-lengthed Sonic OVA movie, in Japanese and English
First episodes of AoStH, SATAM, Underground and Sonic X, and summeries for each series
The Sonic Jam opening animation
Cover scans of all Archie, Fleetway and Manga Sonic Comics, and series summeries for each
The complete Disney Adventures comic series
A museum with official art, including massive amounts of rare conceptual art, with Sonic Gem'esque remixes
Japanese commercials
And that's it...
If this doesn't say that you're a Sonic / Sonic Team fag, I don't know what will.