As of right now, the Dreamcast has the edge.  It has more games, is just as good graphically(better on a monitor), is cheaper, and there are more available.  But that all will change.  Look to see the PS2 end up with many more games, much better graphics, etc.  I own a DC, but that's cause I got it off a friend cheap(system + 2 controller + VMU + jump pack + 4 games for $150!), but if I had the choice(and the money), I'd take a PS2 over it.