The Dreamcast ran various games, Ikaruga, Under Defeat, Last Home, and some others whom's names I can't remember, but basicly as many DC Shumps as I could find ISOs for.
Uhh, the fighters were your typical faire, Guilty Gear, King Of Fighters, Street Fighter, and the Soul Caliber series setups, mostly their 6th gen itterations.
No, Area 51 does not support the Guncon because the PS1 port predates the Guncon's existence, though the similar port Maximum Force does. I used a third party multi-gun that can work as a Konami Justifier, Guncon 1 and Guncon 2. In Justifier mode it works fine. Maximum Force supports both Justifier and Guncon 1.
I actually brought 8 guns total. 4 x Guncon1, 2 x Guncon 2 and 2 x Third Party
And I bought another Guncon 2 in the dealers room, giving me an even collection of 4 Guncon 2's now (I'd left one of the three I owned at home)