1. Memorable, likable characters - each character in this game has so many layers and sub-layers that you can't avoid genuinely caring for them beyond the standard video game parameters. I find myself taking characters with me on quests not because of their strengths, but because I like their personality. This is rare in any kind of game and the last time I felt like this while playing was in Mass Effect 2 (oh hey, another Bioware game).
2. Massive world with tons of content - games nowadays tend to last under 20 hours. This game is just an unbelievably huge world with thousands of quests that are very imaginative and fun to play. I think that the way I'm going, I'll take 200 hours or something before I finish.
3. Compelling storyline and limitless replay value - sure, it's the typical raise an army to fight the bad guy who wants to end the world. But the game presents that classic formula in such a fun way that you can't help wanting to go through it again and again - especially because of the Dragon Age Keep, which allows you to customize the world state. I think that that addition is probably the best thing they came up with - the fact that every playthrough will be different and customizable is absolutely amazing. This is the first game I've played in a long time wherein I can't wait to finish the game just so I can start all over again.
4. Gorgeous graphics and amazing voice acting - lots of love went into the creation of the world and the characters and it shows in the uniqueness of each area. The storm coast is just wet, and you can feel how wet and slushy everything is. The western approach is just so barren, and you can really get that vibe as you walk along the desert. The voices in the game must be enough to cover the voice acting of 10 other games - there's just so many things said in the game and so much effort to convey emotions.
5. Your choices are difficult and they really matter - Everything you do matters in the story. If you choose to side with one faction over another, your entire playthrough is different from the next. The best thing, however, is that your choices are so genuinely difficult. There are no clear cut obvious "better" choices throughout the game. They're presented in such a way that no matter what, you're going to lose out on something. This makes the plot points of the game really intense and important that you can't just scroll through the dialog even on the most seemingly mundane conversations.
6. Fluid battles and varied gameplay - The game's classes and specializations really make you want to try out many different kinds of styles - and in classic Dragon Age fashion, you can switch between characters during battles, giving you all the experiences you can get from each class. The battles are very fluid and intense, with so much variety in strategy that you never get this feeling that you're stuck with a particular character because of his/her skillset. Any (and I'm not kidding) kind of party set up can work. Best of all, the game is actually very challenging if you don't set up your guys properly beforehand; and even then, the game can kick your ass even with 100% preparation (I'm playing on Hard difficulty).
Oh and the freaking dragons really do kick your ass in every way, shape or form.
Probably my only gripe is that there are some bugs in the game that are kind of annoying sometimes - when the game crashes out of nowhere, it makes me want to tear my hair out. But that's just a testament to how good the game is.
This game gets a 9.7 for me. Game of the year, no question at all.