Well, on the PRO side, they added a Mission Mode that gives you more activity to do in the Adventure Fields after you've beaten each of the character stories. The GameCube version (though not the ports, but more on that in a sec) also adds all the Game Gear games as emblem unlockables if you haven't already played 'em on Mega or Gems Collection. Admittedly a pretty good incentive to collect those things, even though you can find the superior Master System versions on Virtual Console now. Oh, and they also lifted the bulk of the Chao system from Sonic Adventure 2 Battle, if you care about that (and fixed the Mystic Ruin & Egg Carrier gardens so they're less broken).
On the CONS: they got rid of the original shading engine for no good reason (it was in working order in a prototype build), and replaced it with something that makes the models excessively shiny and plastic-y, probably in an attempt to mimic the GameCube's cell-shading made popular by The Wind Waker. The developers also gave-up on giving the game a proper face-lift halfway through, so areas like Station Square look different but windows and reflections still show the Dreamcast textures, and there's an obvious clash when untouched Dreamcast models show up like Eggman. The framerate was increased, but unoptimized, so it's very unsteady compared to the original, and there are actually more bugs overall compared to the supposedly bug-ridden original Japanese version. Loading is also slower for the most part (it seems faster at first due to the FPS, but it's an optical illusion).
It gets worse: all subsequent ports are directly built off the previous port, losing certain graphical quality with each version. So the latest version, the 2011 Steam release…is a port of the 2010 XBLA release (also for PSN), which is a port of the 2004 Windows release (that's right, back to PC), which is a port of the 2003 GameCube release, which is a port of 1999 International Dreamcast release, which is an enhancement of the 1998 Japanese Dreamcast release. And yet, even through all these revisions, the Game Gear games are still present in the game data and fully playable, despite the menu being disabled after the GameCube version. Recently, there have been restoration patch attempts for the latest PC version…but at that point, might as well boot up the Dreamcast version on an emulator.
I find that I know almost no interesting Sega games from any era...
Genesis Shadowrun best Shadowrun.
the first one is rough but from the second game on they keep getting better and better gameplay wise, plot wise 2 is the best one
the thing about SA1 is that it feels like it has physics to it. It's not as polished as SA2, but it feels like a 2D sonic game in 3D.
kolibri: quite possibly the best hummingbird based shooter for the 32x
I thought the best version was some PC release after extensive modding and restoration
Is is
Current mods can only fix so much, though. The one that got attention recently, the lighting restoration, isn't so much a restoration is it is a recreation. The guy disabled the modding engine, then looked at the Dreamcast version extensively and wrote his own very hacky, bloated code around the PC version to approximate the original lighting. The result is that it admittedly looks pretty close and much better than DX, but it's not a very elegant patch and drains resources.
Sega really hates Oshima's guts.