There are two seasons to me, winter and not-winter. Winter is an abomination that only exists so that I can better appreciate not-winter. And I do.
In all seriousness, though, it's a tossup between spring, summer, and fall for me. Spring is pretty and everything's coming back to life after a long, dead winter; summer is good and hot with a nice balance of sunshine and rainstorms; fall is nice and mild and absolutely beautiful. I think my favorite times are late spring/early fall, when summer-ish heat is balanced with the beauty of spring blooms and fall leaves.