I hereby nominate you for the office of necro-president.
Does that mean I can get impeached now ?
Sorry - you're going to have to wait another 8 years for that...
Getting back to the original topic - there are three main areas for comparison between the BG series and DA:O.
* Atmospherics (graphics, sound, music, interface) - how well does an RPG suck you into its gameworld?
* Rules systems - how much choice and flexibility do you have to develop a character you can identify with?
* Plot development - how well does an RPG keep you involved, how much difference can you make in the game world?
For atmospherics, DA:O generally scores well. You have an adjustable viewpoint (rather than the fixed one of BG), graphics are generally good (with the exception of textures - I'd strongly recommend installing an HD texture mod or two) and the music is comparable to BG. Areas are reasonably large and plausibly done but you can't enter every dwelling like you could in The Witcher. The major thing missing is day/night cycles - each area in DA:O has a fixed time of day (almost all high noon) which is a particular surprise since DA:O was released after NWN2 which had a particularly good
day/night cycle system with shadows stretching across the landscape at sunrise/sunset.
Rules systems are DA:O's weakness. As Geromino has said, there are only 3 main classes - while fighters/thieves have a greater range of skills compared to their BG counterparts, the exact opposite applies to mages (even though their skills are the more complex in DA:O with the ability of some spells to have a combined effect). You are also limited to a 4 rather than 6 character party (possibly to make this easier to play on console controllers?).
Plot however is more DA:O's strength. The origin stories give you a choice on how to enter the game and play a role further on when you have a chance to revisit old areas/allies/enemies. As well as a journal, you have a codex that collects notes, lore and other background information adding depth to the game. The main plot has some major twists and throughout there are challenging moral choices - do you kill or contain a demon-possessed child? Do you help the dwarves regain a key item even if it means the sacrifice of innocents to use it? How far should a mage be allowed to go in seeking revenge for the loss of his family? There is also huge amounts of character interaction between your partners, some of which is utterly hilarious. When you complete the game - like BG2 - you receive a detailed epilogue showing the results of various plot choices you made.
You then have the Awakening addon included which is a major follow up to the events in DA:O (though it shows signs of rushed development) plus two DLCs (Golems of Amgarrak and WItch Hunt) which occur afterward and expand on parts of the DA:O epilogue.
I've not played DA:2 or 3 since neither are available DRM-free so can't comment on them.