Anyone who doesn't rate Red Rock Canyon is either a curmudgeon or a douchebag. Red Rock Canyon has everything you could ask for from the perspective of a tourist or any avid hiker.
The many turn-off points help to dissipate the tourist traffic and there are enough trails at each to deter clutter along the way. The 13 mile loop is long and windy which makes it fun if you drive a sports car(or if you want to pretend).
13 mile loops are apparently also good for avid bikers because I always see at least 1 or 2 in there even on the hottest summer days. The guys at the front taking your money are always friendly and super helpful and if you get a yearly pass I believe it is $25 which pays for itself after 4 trips. Oh, and the place is freaking amazing to look at. How could I not mention that?