Sonic Adventure 2 is a fan favorite for most of the Sonic community and is getting a full HD rerelease for XBLA and the PSN however searching through a beta website I found out that the game was going to be drastically different than the final product.
http://www.unseen64.net/2008/04/10/sonic...eta-shoes/
The link I just posted states that Sonic Adventure 2 was originally going to have 3 playable characters; Sonic, Knuckles, and Eggman. This was a huge outrage to fans as Tails wasn't set to be a playable character. Also the theme of the game would be that decisions you made would affect the outcome of the game and take you to different levels and ultimately, different endings. This concept would later come to life in the spinoff Shadow The Hedgehog. Speaking of which almost became something entirely different altogether. His originals name would be "Terios The Hedgehog" with Terios literally meaning "reflection of" as he was seen and nicknamed "Dark Sonic" at the time. He was never meant to be playable and would only appear in cutscenes and quite possibly be a boss at some point in the game. Rouge The Bat was also set to appear as a rival of Knuckles like she was in the final game although her name was originally going to be "Nails" rivaling the name Knuckles. Her nails are still important as there what causes her to dig but instead of being her main form of attacking it got switched to kicking, probably in an attempt to make her a more defined rival. Overall I think the changes did good because Sonic Adventure 2 turned out to be the best Sonic game of all time and unfortunately the quality of gameplay only went down from there. While Nails is an understandable name Terios terribly does not fit Shadow at all, well it sorta does a little bit in a weird way. Oh yeah and at the time the deal with SOAP shoes was not yet established so Sonic still grinds but has his normal shoes on.