Demon's Souls - PS3
What K-man said about sums it up perfectly. I still haven't finished it, and this is due largely to the fact that I spend so much time with other pursuits now, and that the difficulty makes it hard to put down for a while and pick back up. But everything else remains true. It's an interesting game that draws on both old and new concepts and puts them together into a compellingly difficult and ragingly satisfying whole.
Borderlands - PC
Brilliant. Take the essence of a run-n'-gun shooter and toss in RPG development, coop play, and random loot drops. You end up with the start of a really refreshingly different franchise. I hope the fixes keep rolling in for the PC... and this is one game where I actually look forward to the DLC because it actually seems (shock of shocks) worth the fucking money.
Might and Magic: Clash of Heroes - DS
If you haven't tried it, you really should. It isn't perfect, but that's mostly because it lacks some of the more RPG-ish aspects of Puzzle Quest. Still, it's got a fun little story, some absolutely brilliant sprite work, and some truly addictive gameplay that rewards your thinking skills a lot more than many similarly-styled games. Probably the best thing I've played on DS all year, and I've played an awful lot of good DS games.
Honorable mentions:
ArmA II - PC
I haven't really had the time to get into this too much, but what I've played so far has been absolutely fantastic. Yeah, the voice acting is totally bogus, the radio-chatter system is really wonky, and there are some very strange graphical quirks that occasionally make you wonder, but as far as military simulation goes, I don't think anything holds a candle to this. It's realistic, well-paced, and despite the problems with the acting, it actually builds a compelling and very human story that makes you care about the people you come across. I imagine most people will look this game over, and still others will be daunted by the huge list of commands and steep learning curve, and even others beyond that will pass it over because of some of the bugs or slightly off-kilter design... but if you've ever loved a game like this, you owe it to yourself to give it a shot. I'll know more when I have more time to put into it, but this is something truly unique that I've really enjoyed and heartily recommend to anyone willing to sit down and give it a chance. The story, the multiple ways you can take the campaign, the fantastic locales, the wonderfully rendered terrain, the multifaceted and deep gameplay... this game has so much going for it.
King Arthur: The Roleplaying Wargame - PC
Another interesting game that takes different elements from different genres. Ultimately, it's a super-gorgeous, deep, rewarding strategy game along the lines of the Total War series, but focusing on Arthurian legend with some added bits of fantasy. Released on Steam currently, but hopefully to get a retail release sometime in early 2010, this is something any fan of deep PC strategy should look into. The developer seems to be taking time to listen to fans and add new stuff and balance changes in regular patches, too, and the community is pretty active. This one could go places. I wish it great success in 2010 and will be buying any retail release I can get my hands on.
Guild Wars - PC
Because it's still fun, it's still beautiful, and we still go back and get sucked in for hours even when we just plan to do one simple thing or other. I still haven't gotten anywhere near where I really should have, but we're finally nearing the end of the first campaign. It didn't come out this year, but it's still one of the best games I've played this year, and I've still played a pretty good lot of it. Now that I've got a big, beautiful widescreen monitor... so much the better. Though now my screenshots take up a ridiculous shit-ton of space. I need to hurry up and get my new terabyte hard drive installed, and fast...