The ideal gym lets me continue my workout routine uninterrupted. But that is rare.

Dumb bells over 50 pounds are important. Again, a rare sight. A nice array of universal equipment is also a plus. All decent gyms seem to have bikes/aerobic, though some lack on quality.

I like the Reebok Sports Club combos, so:
-RC BC
-RC DC (22nd), though it was a charge when I was a regular here 1-2 years ago
-FS SFO
...might be one or two others...

Others that come to mind that I like:
FS Tokyo Mar
Park Hyatt DC- sort of dingy setup, but nicely equipped for a small gym
FS Chicago
RC SRQ
MO DC
London NYC