Yonge Street Fitness is an undiscovered gym-gem. It's downtown, clean, reasonably-priced and has all the weight equipment and cardio machines you'd be looking for.
The two things that stand out for me about this gym are the natural light -- big windows and actual living plants shouldn't really make you happier to work out, but somehow they do, and the fact that there's so much space.
You don't have to stand in line for equipment at any time of the day. even after work (unlike a nearby gym where a friend complained that in the change room at lunch time there wasn't enough space for her to bend down to put on her shoes.)
The fitness classes are good-quality in terms of the instruction and also small in size, although not as numerous as at a mega-gym or boutique fitness studio. "Cyber-fitness" videos play pretty much all day in in the studio in case you want to join in (no one actually does.)
It's not a chain and has non-draconian membership options. I initially pre-paid for a six-month term and bought another one today. As should go without saying, the members are diverse and attitude-free. If you're looking for a downtown gym, give this one a shot, pump, jump, pedal...