oh god... where to start.... (i'm a dreamcast junkie)
jet grind/set radio ("set" in PAL and JAP, "grind" in U.S.)
phantasy star online (don't know if many still play, best to ask around before a purchase)
shenmue (stunning, stunning, stunning)
shenmue II (likewise)
skies of arcadia (superb)
unreal tournament (good port of an excellent fps)
soul calibur (duh)
rez (you have to play this game)
resident evil: code veronica (likewise)
grandia II (great game)
sonic adventure (it's sonic, nuff said)
sonic adventure 2 (likewise)
headhunter
marvel vs. capcom 2
crazy taxi/ct2
space channel 5
and many more. some ign writer best summed up the dc with this...
"the candle burns twice as bright for half as long"
it is a shame it didn't get the support it did... imagine it now with PDO, JSRF, SMB, Beach Spikers and many more. it would be unstoppable, sega's dreamcast days were arguably some of their best in terms of output with consistently innovative and consistently excellent titles. enjoy gaming heaven.