I'll second (or third) Slow's for BBQ, but they are right about getting there early in the day...I have friends who had to wait for a table because it was so packed and if I remember right they don't do reservations.
Hockeytown isn't bad but it's definitely crowded after a game. I can't do Greektown - the noise and the crowds get to me, and even though they say no smoking, it's just awful there. I almost have to hold my breath walking through to get to the People Mover.
Hockeytown Authentics is always cool. I'm due for a visit there one of these days...it's been a while.
But whatever you do, have fun!