The only one I am familiar with is San Diego. In San Diego I’d rate their bus system a C+ and their train system an A-.
The busses generally aren’t that great as they ran late a good deal of the time, however their train system was amazing. If you had to go anywhere in midtown, or if you needed to go from east to west or down south then the train was great. However going from La Jolla down to the train was crappy as the express bus only ran during business hours and the other busses took forever. I remember once trying to go from La Jolla to a place downtown. Driving took me about 15 minutes. I spend 2.5 hours using the bus system.
I have heard Boston and NYC have the best public transit systems. I would assume another city like SF has a good one too.