I voted for the VC.

I've had my Wii longer than my 360, but I'll still have to say XBLA. I liked the concept of the VC, and have a few games, but the pricing is atrocious, and some of the games just aren't that good. If I'm going to spend ten bucks on a game, I'd prefer it to be a new game, rather than one I played ten years ago and still have on cart upstairs. There's some classics on XBLA, but lots of original content as well.
Add in playable demos instead of just screen shots, online play, achievements, and HDvideo/DD sound, and XBLA gets the square.

Those old, poor graphic games built this industry. A good game is a good game, regardless of graphics or the year it was released.

My opinion - It's like buying vintage wine instead of a draft beer.

I was iffy on the VC at first, but Super Metroid, Paper Mario and Sin and Punishment put the VC miles ahead of PSN.

While I'm no fan of the PSN and their inane payment system, I must say that you get tremendous value when you can buy a quality game like Medieval, Crash Bandicoot or Spyro for a mere $5.99 and be able to play it on the PS3 and the PSP. Best deal in old-skool gaming, IMO.

Many of us already have all the classic NES/SNES/N64 games that we want. If VC was the only place I could play SMW, Super Metroid, LTTP, Mario 64, SMB 1-3, etc, my vote would change. But since it isn't, my vote goes to XBLA, and it isn't close.

VC is nice but demos help XBLA win by a huge margin. I am sure a ton of people have bought a game on VC remembering how cool it used to be and then after playing it once they realize it was better 10 years ago or more.

Nintendo makes great games but not everyone can go back and enjoy them. Giving demos would probably cause a fair sized drop in game purchases.

There are a number of games on XBLA that I keep in my list just as trail games because I am cheap and they are still fun to play.

The Playstation Store is a joke in terms of prices and content. Other than flow I never saw anything there work getting.

I went browsing through the PSN store tonight to pick up the PS Eye software, and while they've made slight improvements, it's still a total mess. The navigation is unnecessarily difficult, and most of the content is video and trailers. While I do love the PS1 games that I can play on my PS3 and PSP, they don't offer nearly enough, and like many people have said about the VC, a lot of those games don't hold up anymore. So, for my money it's still XBLA in first, VC second, and PSN in a distant third.

Of course, if I had a PC Steam would be first. :)