i've lived in Boston, NYC, and SF.
hands down my fave is Boston for riding.

so... many... options... to get anywhere and everywhere in Boston/Cambridge. the layout of the city is so messed up that you always have advantage over cars. public alleys. flatness. dick drivers that don't give a **** about you (as opposed to SF, if you ride in between lanes these drivers don't know what the hell to do with themselves). riding along the river. over the bridges.. etc etc etc...