Campisi's for Italian (see if you can meet Amber the Playboy Playmate!) on Mockingbird just West of Greenville.
Tons of stuff on Greenville Ave, the Grape is nice - fine dining right next to The Dubliner bar, Greenville Bar and Grill is accross the street and has very good food. Teppo for Sushi is the best sushi I've had anywhere in this country so far - it's also on Greenville.
If you want middle of the road stuff, Aw Shucks on Greenville is fantastic seafood - cajun style. There is a Melting Pot that's fondue. Blue Goose for mexican food if you want.
All of that is on Greenville Avenue South of Mockingbird (Lower Greenville as it's called) and there is also a ton of stuff further up North on Greenville - like 3 forks that HotWls mentioned above, as well as many others. Edit; III Forks is over on Dallas Parkway (the Tollway) but there is another good steakhouse on Upper Greenville...can't remember the name off hand.