Loveland/Keystone/Copper/Breck are all about the same distance, around 60-90 mins.. Loveland is known for its freeriding and its mostly locals. Keystone A51 park and not much else. Copper I don't know much of and Breck seems to be the most resorty of the 4 but has very nice parks and pretty good freeriding
Vail is an hour further I think and its parks arent too good but their back bowls are awesome
Echo is the closest to denver but its pretty tiny..