Hands down, LGA is the worst. Congestion is impossible. Other challenging airports in North America are IAH (dreary), MSP (concourses are too long,) BOS and MIA, Connections are tough. PHL is lousy also.
I'm not a big fan of YUL either. The best? I like SLC, RDU, LAX, and LAS, 'cause there's something to do on layovers.