I'm 99% sure most people believe that "pop" music is top 40s music but it's so much bigger than that, I'm a big fan of pop music, but that doesn't mean I worship at the altar of Lady Gaga.
Pop music to me is a sound which is represented by the auto-tuned Ms.Spears but more happily represented to me by pop bands like Rilo Kiley, Belle and Sebastien, Passion pit, Alphabeat and Postal Service. There's been amazing pop music throughout history, and I couldn't pull out an era which had the best "pop" there's some great pop now, but theres almost an endless catalogue of classic pop. It depends on your sensibilities, like I'm a huge wall of sound fan (oh dear Phil Spector) so that era is a great source of music for me (especially anything Larry Levine worked on *swoon* - Pet Sounds! )
I liked the last Gorillaz album (well actually I thought it had some great high points, but was over collaborated in several places, a touch of self indulgence I guess) and I think On Melacholy hill is a good song, I'll have to spotify the album
P.S Passion Pit's Sleepyhead is my summer of awesome song right now