After playing both games countless times, I figured I might as well write up a comparison review between Dragon Age: Origins' 'Return to Ostagar" and Mass Effect 2's "Normandy Crash Site" Downloadable Content. Please turn away now if you don't like spoilers.
At the start of both games, your character is involved in dramatic events.
Dragon Age: Origins - Your character is saved from their circumstance, (Each custom character has a "Origin" story. Hence the name.) made into a Gray Warden and has the man who saved you and the man who didn't judge you, brutally killed. (One crushed to death by an Orgre, while the other is swarmed by a hoard of Dakrspawn.)
Mass Effect 2 - The Normandy is shot down by the Collectors. This forces everyone to abandon ship. (Some cannon fodder crew members die) Sadly, in saving one of your crew (Joker) Shepard dies. (But as we know revived at the start.)
I'll start with "Return to Ostagar" -
Even though you can access it when you leave Lothering, I recommend not going there until you have at least recruited Wynne, as having her in your party (Along with Alistair) makes for interesting dialogue and makes the story progression feel natural. The DLC location itself is flagged up as "Bann Loren's Lands." on the Ferelden area map. After going here and meeting someone it will then prompt you to (as the DLC is dubbed) return to Ostagar.
When you return to the site you see right away how the place is in pieces. You'd expect it to be a state after you left. But to actually see it how it is, it kinda brings a sense of down-to-earthness about it.
Upon your arrival you have to fight some Darkspawn and find a piece of King Cailan's armour on one of the bodies. Thus you get a quest to get all of Cailan's equipment back. As you make your way through the ruins of Ostagar and battle Darkspawn, you find a plot twist, that makes you dislike Loghain even more and more of the equipment. Then about half way through the DLC, you will find King Cailan's body, strung up and impaled. As your party look up at his dead body, the game plays a soft version of the games theme tune and gives you a short montage of him while he was alive, which just gives a somber feeling. After hearing what Cailan was like from others, this will be a sad moment, because you knew he died. (We are give a cut scene both when it happens and during the montage.) But to see him strung up like that, then shown a reminder of how brutally he died. That will make you feel something.
After this you are then confronted by a Darkspawn Necromancer. You have to chase after him AND gather all the pieces of armour that are missing. Once he is cornered, you then get to kick his ass and the ass of the Orgre who killed King Cailan. Once the battle is over you then have all the equipment and return to Cailan's body.
Alistair will then make a query on what to do with his body, since it just doesn't feel right leaving him. You then have three options: Give him the traditional pyre which all nobles have once they die, take him down for the wolves to feast on or just leave him there to rot. I personally gave him the traditional pyre since I felt he deserved it. (I know we don't know him for long... but he was a really nice guy.)
After all this the DLC is then over.
Now for "Normandy Crash Site" -
After going to the Citadel, (and having your Spector status reinstated) Alliance Command will send you a message asking you to retrieve the dog tags of the fallen crew members of the original Normandy. You can then go to the planet "Alchera" which is when the DLC will begin.
Once there, it plays eerie music and it gives off an uneasy feeling being in the debris of the Normandy. It almost feels like the odd feeling you get when walking through a graveyard late at night. There are no enemy's around, but you expect something to jump out at you any moment. While you’re there, you collect the dog tags of the crew members who died with the Normandy. While collecting the dog tags you go to different parts of the broken Normandy and get flash backs of crew and how the Normandy once was. Before or After all this you can place a Normandy memorial marker. Once you are ready you can then leave.
DLC is then over.
Now with all that in mind this is my personal opinion.
Both of the games are great in their own right, and even though they were made by two entirely different sections of Bioware, you can tell they put a lot of thought into doing both DLC's. However, I felt that the Dragon Age crew put more effort into giving fans some closure, while the Mass Effect crew, to me, it just felt like they threw it out there for the hell of it. It didn't really feel like closure, but more just putting it out there since they know fans would want to know what the Normandy looked like. Where as the Dragon Age lot KNEW that fans would want to see Ostagar again. That is where it all began.
So overall, I prefer the Dragon Age DLC. They were both well written, but I just got a sense that more attention to detail was put into "Return to Ostagar" than "Normandy Crash Site."
With "Return to Ostagar" I enjoyed collecting the armour and getting payback for what the Darkspawn did to both Duncan and Cailan. It gave me a sense of victory and closure. It also gave me more determination to take down Loghain and Howe.
With "Normandy Crash Site", I was left wanting more and didn't get the closure it was trying to give. I would have liked to shoot the crap out of some Collectors, even though you do get revenge in the final mission. I still would have wanted more than justwandering around a frozen wasteland gathering dog tags and getting memories.
Anyway. These are just my thoughts on the DLC's. I encourage you to get both, because they are worth the playthroughs.