Romantic/Drama/Comedy, it's far from a chick flick. I thought it was going to be a light hearted chick flick at first, so I can see why your guy friends said that. But when I watched it, it didn't have those horrible clichés and the typical set up of a chick flick. It made light of them if anything, the karaoke scene singing Train in Vain.
far from a chick flick, chick flicks are what they are. 500 Days of Summer explored things much more deeper than boy meets girl and all of that bollocks, it explored fate, it showed how things can collapse and change. It showed things people can relate to, chick flicks show things people want to relate to. To me, 500DOS is far from a chick flick, just the same as Titanic - it shouldn't be classed as a chick flick even though it is.
I like some that are quite light hearted, The Full Monty for example... but they have to be well made. Richard Curtis is terrible.