Bioware has been making the same game over and over again; the same basic plot structure, the same characters, etc. etc (I won't go into details but any Bioware fan knows it's true). If you don't mind that, or never played much Bioware titles, you won't mind at all.
My opinion is that Bioware devs were/are getting sick of their own games, and tried to do something different with Dragon Age.
The first Dragon Age imo was okay. Masses praised the game, but I think much hype was involved and it was played by many people who weren't into RPGs, and by comparison to other popular games (obvious example: FPS games), RPGs are in general far superior. BTW that what I think also happened a little with DA2 - I mean even Two World will seem great if you never played an RPG.
The thing Bioware devs wanted to do with Dragon Age Origins was tell an original, non-linear and epic tale, set on a very dark dark and mature fantasy-universe, with charismatic companions, and a very class-balanced combat system with a huge focus on strategy and tactics.
While I don't think they completely failed, the story wasn't that original, it completely loses focus (ex: a blight is invading the country, you're the only grey warden alive, you need to stop it at all costs... so you decide to go on a quest to find mystical ashes from a dead prophet to cure a dude so he can back you up to turn the nobility against another dude who turned himself king); although there are some important choices mid-game only two origin stories make sense and they all converge into the same plot after the turorial quest.
The dark tone and maturity of that universe makes the game a Witcher-wannabe and shows the game had different development stages (look at the first early CGI trailers and the final product)... I mean ketchup-blood all over your body doesn't make the tone of the game darker and in-your-face sex doesn't make it more mature; the game wants to be grim so bad sometimes it's silly and, to make things worse, it isn't.
Besides the voice acting, I wasn't particularly impressed with the characters because they're just 'copy/paste's from many other Bioware titles; the combat is a mess, and when devs realized their masterpiece combat system was a poorly imagined D&D-copycat failure, they decided to somehow fix the issue by making it insanely difficult...
They tried to not fail so much with Dragon Age 2. But they failed even more, to a whole new level.
DA:O looked like shit and felt kinda generic - DA2 looks more or less the same, textures look particularly worse, scenes/levels lack detail and artistic input, places feel empy and at the same time claustrophobic; they changed one or two things in one or two character/race designs, but everythink as still the same look, so it's weird. So, now, it looks like shit and feels like a poor effort.
The combat didn't work that well in DA:O - some moron at Bioware thought that adding cooler animations would fix things, and what the game was really lacking was "enemy wave" system (people also complained about not having a high camera, but that's stupid because it didn't make the not-that-strategic combat system of DA any more strategic). So, yeah, DA:2's combat system isn't all that great again, but now it's like devs don't even care.
The loot - devs tried to make things more immersive and personal in DA:2; they failed at every attempt: one of those is that empty, boring and pointless house with those three/four static persons; another one is not letting you change your party's gear - that's retarded. It's a terrible execution of a (maybe) good ideia that also ruins things like looting (you get tons and tons of gear and you can't use 70%). Again, you need to be a moron to come up with such things.
The levels. I won't even get into that. That's the main thing everybody complains about.
The story - nobody here thought "Wow! Merrill dialogue sounds exactly like Tali's from Mass Effect"? This is the laziest work from Bioware yet; there's no real story, many things just don't make sense (try playing like a mage), the ending is anti-climatic, the characters are dull, the gay options feel brute-forced into the game, the story within a story thing was a waste (they ONLY FUCKING used it to make a gag-level with Varric... WTF!?), Varric isn't the rock-star they want him to be, the Mass-Effect-style dialogue system could have been good if the dialogue options weren't inferior to those of Mass Effect.
Framerate drops; the scenario repetitiveness leads to lots of backtracking; the import-save system was only used to make two cameos/gags; major retcons depending on your choices in DA:O (ex: Leliana's head, Flemeth cloned herself, etc.).
The game isn't bad... but it's clearly a disaster, and it caused a huge hate-storm from fans of the previous game.