DA2 was an odd sequel. In some ways, it made huge steps forward. In others, its like they completely forgot what made DA:O great.
If you compile a list of the stronger and weaker points of one game, you can pretty much just flip it to find the same for the other.
I think DA2 had better characters (and definitely did a better job at building them), but DA:O had the better story. DA2 had more exciting combat, but DA:O's was much more strategic. DA:O had several environments, DA2 only had one. But DA2 more thoroughly fleshed out the feeling of that one area than you see in anything in DA:O (including Awakening, which heavily features just the keep and Amaranthine). Art is better in DA2, but they used many of the models from DA:O (particularly because DA:O required more new models). DA2 will send you to the same dungeon map nonstop, which was less egregious in DA:O.
Only thing that's a solid pro for both, imo, is that the music is great.
So which game you think is better is going to depend on what value you place on various aspects (along with the cons, for instance). The main reason I play RPGs is for the characters, so I like DA2 a lot more than many other people do. The loss of some of the strategy wasn't such an issue for me, because that wasn't my favorite aspect of DA:O. Repeating the same dungeon was irritating, but not something I personally hated enough to detract points for.
I DO think the narrative of DA:O was better overall, primarily because it is a unified plot. DA2's is mainly just about the protagonist, which makes it feel like cobbled together short stories.
But I also prefer Hawke to the Warden by a significant portion. I like how they went out of the way to create 3 distinct personalities for him/her. I like that I have free choice there, and the fact that I actually felt way more like I was making real decisions about characterization.
It's just not as significant to go through DA:O going "lolchantry" or "Die mage!" at every opportunity as it is in DA2, especially if you replay it. Diplomatic Hawke and Sarcastic Hawke actually feel like completely distinct characters.
So, if what you like is the strategic gameplay, diversity of the environment, overarching narrative, ability to choose your Origin (/play as a Dwarf or Elf), and a non-voiced protagonist, you'll prefer DAO.
If what you like is the character development, art, ability to choose your personality, faster combat (like at lower difficulties in DA:O), and a deeper investment into the story of the main character, you'll prefer DA2.
As for the two of them vs. ME2, IDK. I love both series. I guess I'd favor ME, but I have to say that a huge part of my love for the games are because they filled a significant Space-RPG void in my heart. I love DA, but fantasy RPGs are much more common.
It'll be close, but Romney has the momentum.