The VMAs were good when MTV didn't know any better. Now, as SP points out, there's this overriding sense of "we gotta create a water cooler moment with something outrageous and spontaneous," which of course means that whatever happens has been plotted by a bunch of stiff suits.
Madonna writhing around the stage in a wedding dress singing "Like A Virgin" was memorable because it announced, without a doubt, that she was no no one-hit wonder. Madonna locking lips with Britney Spears and Christina Aguilera? A tired and desperately pathetic act by a has-been.
The Dice Clay thing was great because it's not everyday you get to watch a guy commit career suicide on live TV. MTV proved what a joke it really was when it tried to be everything to everyone and failed miserably in 1989 when it ironically gave best video of the year to Neil Young's "This Note For you," which it wouldn't air because it made fun of the rampant commercialism that pays the bills on MTV.
When Janet Jackson ripped her shirt to show her black bra for two seconds during the 1990 VMAs, it was surprising because she'd crafted such a goody girl image up to that point and this felt like the moment when she started crafting a more adult image. But there was a certain goofy charm to it that was quite obviously missing when she flashed her enhanced tit at the MTV-produced Super Bowl halftime show.
There's Axl Rose, noted gay basher, playing November Rain with Elton John, and Pee Wee Herman showing up a few weeks after he was arrested for whacking off in an adult theatre and saying "Heard any good jokes lately?" and Nirvana saying screw you to MTV And playing "Rape Me" instead of "Smells Like Teen Spirit."
And nothing that happens tomorrow will top the sheer sizzling power of Pearl Jam and Red Hot Chili Peppers performing "Jeremy" and "Give It Away" consecutively in 1992.
So anyway, to answer your question, yes it used to matter, but now, like everything else on MTV, the VMAs are irrelevant to anyone over the age of 19.