I'm going through my first playthrough of Dragon Age Origins and I'm not disappointed so far. Despite the number of hours put in, apparently I've only finished 33%.
For me, it actually does feel like the spiritual successor of Baldur's gate 2. I don't have the nostalgic feeling of playing baldur's gate since I only played it about 6 months ago and haven't even finished it yet. Honestly, both of the games really play similarly.
1. I can't say I'm relatively new to the genre, having played even a bit of curse of the azure bonds way before. But the first game of this type that actually finished was Icewind Dale II. Not much story, but I miss the game more than the others (I even stopped playing planscape after an hour into the game). I definitely think nostalgia is a huge factor.
2. I think most of the people are simply complaining about the lack of characters available. Either it's limited to four players per team or there are only 9 or so companions available. But I honestly think it comes down to the lack of customization that may fail to add to replay value.
I myself am into powergaming, that's why I almost always pick rogue as the class for my main character - there's experience in traps and extra gold in chests. However, what I like about Dragon Age Origins is that it is a very forgiving game. Unlike Baldur's Gate, once a character dies, they die. Ressurection is quite a hassle for me causing me to reload instead. There are experience penalties to whoever is or is not in your team.
I think Dragon Age remedies this quite well. Everyone gets the same level of experience whether or not they're dead or not in your party. Because of this I don't feel the need to be bound by the Tank-Rogue-Mage-Healer Formula. It's okay if I have four warriors because most of the battles are balanced anyway especially if you use the right tactics. The battle system in essence allows for a degree of flexibility from the traditional team set-up. And If I do get bored with a current team, it's easy to replace them at camp because they all have the same level and are easily accessible.
The tactics system makes me more comfortable in what companions do as well, making micromanaging less of a hassle. (I think to target a cluster, there is the enemy has number of allies option?)
3. Sidequests: I honestly can't see the distinction between all these games. I felt that Baldur's gate sidequests were also fetch it - go back quests and battle this there - come back. If there's a red dragon maybe there's flemeth (also there's a bug with her - she didn't attack me after killing Leliana

).
4. Character development - Relatively the same but it has the approval system which is a nice touch. The gift system can be abused (I have Morrigan, Alistair, Wynne, Lelliana, Sten, Zevran hovering at around 100 currently), but you have the option not to use it at all to fully reflect your choices throughout the game.
All the character's in Baldur's gate and dragon age origins are caricatures in one way or another, but I feel that Dragon Age Origins particularly excels in voice acting and subsequently better develops their characters. The script can really be humorous in some sections because of the manner of its delivery. (Female Edwin is still a blast of course

)
5. Graphics - I don't play games like these primarily for the graphics anyway. If graphics were the prime consideration then DO definitely wins over Baldur's, Planescape, Icewind Dale etc. But it is sufficient and character expressions are good enough to similarly convey feelings and the mood.
6. I just can't help but notice a lot of people limiting themselves to the traditional formula. You don't need an attack mage. A healer can be helpful, but you can just make the character into an arcane warrior just as well and make the healing a minor function regulated by the use of good tactics.