Uplink and Darwinia are nice. Warcraft 3 ist fun too (and the Windows-CD works for Mac as well, except for one edition, where they kind of - forgot to put the Mac-Files on the CD)
But I can't seem to get Starcraft to run, it should work in Classic Mode, but it simply doesn't. What a shame, Starcraft > all.
Ah yes, and there's an active Freeware / Shareware-Community. Google around for Ragdoll Soft (N-Ball!) and "And Round Again".
Most of the other Windows Ports suck (bad performance, Knights of the Old Republic runs barely on my 1,33Ght PowerBook), but if can get them running, you still have to keep in mind that Multiplayer rarely is cross-compatible. No Rise of Nations MP = teh suck.