The last great Sega Console was the dreamcast. It is still legendary for its perfect arcade ports. this was possible due to the fact that the Naomi Arcade board was the same as the DC but with more memory

There is no good Dreamcast emulator for the Mac yet. Still LXDream, a Linux based Dreamcast emulator is working on OSX support (probably intel macs only though). If oyu have an intel Mac, you could consider booting up in XP.

A nice blog with lots of things about the Dreamscast is the Dreamcast Junkyard

My personal favourite games are.

* Samba de Amigo
Rhytm based and lovely

* Crazy Taxi
Great Arcade port of taxi simulator

* Gigawing, important shoot'em up that redressed the balance between player and enemy. See here for more details


* Densha de Go, Arcade train simulator