....I don't know what upload sites your database will allow, Nightcrawler gave a link once, but that was after April
Meantime, I got some Qooy redirected depositfile links for some Sonic/2 hacks:http://qooy.com/redirect/1OSMQHMW/4
^called "Robotniks Revenge" for Sonic 2; Author goes by ColinC10; levels, graphics, and gameplay are changed, guessing text as well, to make it a complete hack, since the title screen says "time attack" "survival" and allows you to pick between Sonic and Tails. If that didn't give the hint, it's a boss rush using all the bosses between the first 2 Sonic games.http://qooy.com/redirect/1KRDXVFX/4
^called "Sonic 1 - Return to the Origin," obviously for the first Sonic game. Author is Carretero. Far as I can tell, it's a level hack, and nothing more. This has you play the levels in the same order, but backward, from right to left. Makes it more challenging when you're used to the stages as they go from left to right.http://qooy.com/redirect/1PTI1CLR/4
^This one is called Tohaka, it's for Sonic 2. Author is either just Ultima, or the group he put together called Shadowsoft games, unfortunately I have no idea there. Seems to also just be a level hack, though the title screen is changed, if that counts for a graphics hack. Pretty much makes a new game out of Sonic 2's levels. Oh, it's need to be played more to tell, but I don't know if any gameplay changes occured. The site I go it from mentions that it was the intention, but I didn't play far enough to notice anything.
That's all I got for now. You can google search Ultimate Mortal Kombat 3 Trilogy, and you'll come upon a site that has an incredible UMK3 hack, in patch format, as well as pre-patched rom. I seem to have a much older version of this. It also requires it's own hacked genesis emulator, not sure if including that, or just that fact alone, would have been against the rules or not.
You can find a ton more, though as pre-patched roms, Sonic hacks at a site called Sonic Retro. Those 3 just stuck out more to me, out of what I have seen(that's not already here), but I probably still haven't seen the best of what's out there
I can make it into a patch easily enough(I think..), thanks to I.S.T.'s mention of Lunar IPS, but I can not find who the author of the patch is. One of you guys had a youtube video not too long ago, that included a link to the pre-patched rom, of a hack called Mario vs. Airman, which is a SMB hack that puts Mario in the MM2 Airman stage.
Lastly, knowledge of tools like Lunar IPS really needs to get out there. Good potential for getting more hack patches up on this site.