I've had all three consoles for most of the generation, though the PS3 was last. I'd rank them as:
1. Wii - like the Gamecube before it, I found this to be the console where the quirkiest stuff that fit my own tastes landed. The hesitance of Japanese developers to adopt HD left a lot of the smaller, more creative games on this system and I love it for them. Just a casual glance over my collection and the number of not-always-AAA-but-all-worth-playing games is substantial. A Boy and His Blob was charming, fun, and beautifully animated. Fragile Dreams was a little janky but had some of the most moving moments in any game I can remember. The Klonoa remake was stunning. Lost in Shadow was a beautiful swansong for Hudson. Muramasa isn't perfect, but it sure as heck is also fun and gorgeous. The Wii Prince of Persia game was GREAT if you like those (and an entirely different game by a different studio than the 360/PS3 one). Rhythm Heaven Fever is some of the most fun I've had with a rhythm game since Ouendan. Silent Hill: Shattered Memories I find absolutely brilliant as an experience even if it feels different from the rest of the series. The Trauma Center games make GREAT use of the remote. Zack and Wiki is a wonderful throwback to old point-and-click adventures.
Of course there's a lot of other stuff that's not exclusive but still fun. The Wii has the best version of Resident Evil 4, and it also gave me the ability to play Sam & Max on a console for the first time. I had my first encounter with Broken Sword there as well. Obviously there's the big Nintendo stuff too, and I feel that Nintendo as a first party has been better than they've been in a while this generation. Mario Galaxy 1 and 2 are my favorite 3D platformers ever. NSMBWii is a MUCH better game than the DS original and amazing fun with friends. Metroid Prime 3 closes out that trilogy in brilliant style. Smash Bros. Brawl wasn't as good as Melee but is still solid, and I've put more time into Mario Kart Wii than any other game in that series. I skipped over a LOT of games and focused on the highlights, but even dependent on one's tastes, I have NO idea how there are gamers who just think the Wii is worthless (granted there are those who say that every console is crap, even ones I also love like the PC Engine, Saturn, and Dreamcast).
Because it's so amazing it deserves its own section: as far as I'm concerned, Xenoblade is the best RPG of the generation, and one of my favorites of all time. It hit ALL the right points for me in terms of what I'm looking for in an RPG and now there's finally one that outdoes Skies of Arcadia in the adventuring/exploration department. And the thing is - the game NEVER WOULD HAVE HAPPENED if it weren't for the Wii's underpowered-ness. Would a game so massive and ambitious ever have been greenlit by another publisher for an HD console considering how much that would've cost? Probably not. So screw resolution - the game outdid anything on the HD twins with crappy 480p graphics but a heck of a lot more soul.
2. Xbox360 - NEVER saw this one coming after last gen. The original Xbox never enticed me enough to pick one up, even with the Rare purchase and some good Sega exclusives. The deal with Mistwalker at the beginning of the generation and the promise of Rare's work got me on board early (too bad Rare's output was... iffy at best).
Highlights of the 360 for me: Kameo is a super fun adventure game and Rare's best post-Nintendo work, in my opinion. Blue Dragon and Lost Odyssey provided the experience that I would've wanted from FFXIII and did not get. Gears of War is a lovely guilty pleasure for me - everything those games ooze reminds me of what I hate about "gamers" and yet they're fun. Infinite Undiscovery was fun for me even though it's considered bad by everyone else. Tales of Vesperia was a lot better than I expected.
Mostly the 360 was the place where I picked up multiplatform games since I always looked into what was objectively better on it vs. the PS3 and for most of the generation developers were BAD at PS3 games, apparently. Stuff like Bayonetta, Bioshock, Child of Eden, GTA4, Nier (my OTHER favorite RPG this gen), Mirror's Edge, and Red Dead Redemption found their way into my collection for this console. Portal 1 and 2 didn't hurt, either (love love love).
My only disappointment with the 360 is that it came out of the gate strong with Japanese developed games and for the past several years there has been nothing of consequence that I've cared about from Japan on the thing. Oh well.
3. PS3 - It's turned itself around substantially from the beginning of its kind of sad life, but it's still my least favorite of the 3. MGS4 was merely okay, Uncharted was a disappointment for me (the sequel was much better but I still consider it the summer-blockbuster-popcorn-fluff, all-style-little-substance of video games). Likewise LittleBigPlanet really didn't do much for me. My favorite exclusive is probably 3D Dot Game Heroes, which is a lot of fun. Katamari Forever was much better than the 360 game, but still didn't capture the greatness of the originals. As far as non-exclusives, El Shaddai was cool and quite creative. FFXIII was better on PS3 than 360 but, well, you know how that polishing-a-turd adage goes. Also picked up this version of Rayman Origins because the dualshock is WAY better for 2D games (though I much prefer the 360 pad for analog games).
Looking at just my disc library, the PS3 seems like more of a dud than it should, so thankfully other aspects of the console somewhat made up for it. One place it did excel for me was downloadable games. Flower and Journey are two of my favorite experiences of the generation, and the console became my go-to for Telltale stuff. I also have a 60 gig model so it's nice running PS2 games on my plasma via hdmi. Looks much better than through the PS2. It's also been my Blu-Ray player of choice, which has been lovely.
So yeah, that's where I stand. But as I always say, I'm well aware that my gaming preferences are not those of the general population, so disagreement would not shock me in the slightest.