Depends on what you like. I'd personally go either Dragon Age or Mass Effect, but which one really depends on your gameplay style.
Dragon Age is your classic top down RPG (Or third person, dependant on where you keep your camera). You don't button mash (in Origins and Awakening), you have your classic classes with specialisations that can be unlocked by talking to people or buying books, you have a health and energy bar, and your spells are in a hotbar for you to press as about your only interaction in the combat with the exception of telling your party what to attack, and where and when to move. You can control each of your party members individually. Some sections of the game are a bit brutal if your not prepared for them, but all round its a great game. Awakening continues the game with a new story, still with your character, some new abilities and weapons and that sort of stuff. There is the occasional bit of problem solving in both games. The only glitch I encountered was in Awakening, and it wasn't game breaking in the slightest. There was one ability that allowed you to keep quickly attacking an enemy until you ran out of energy (Infinite Flurry I think it was called), however, my game glitched when I used it and whatever I was attacking got stuck and kept repeating its attack animation whilst doing nothing until I stopped using the ability. Made everything very easy to do, but felt a bit like cheating. If you get the GOTY addition, you also get a lot of DLC. Some of it is used in the bad way, taking things out of the game for those who buy used, but the far more substantial DLC was the good kind. Things Like Leliana's Song, Darkspawn Chronicles, Golems of Amgarrak, and Witch Hunt all added new content to the game in their own, very short, campaign. But yes, long game is long. My first playthrough took me 120 hours to complete, doing all sidequests and exploring every corner and getting every secret weapon of course. The 'moral choice' system is the best I have seen in a Bioware game I have played though, and the dialogue system is not in a wheel that will tell you which option is right. You'll occasionally get hints (Thanks to options being labelled 'Persuade' or 'Intimidate' and such), but you have to think about your responses to be nice to people, not just always pick the top left.
Mass Effect has the inventory and level up somewhat similar to older RPGs, but the combat is primarily third person shooter, with a number of abilities that you can blast out whilst doing so. I encountered a couple of glitches where elevators wouldn't work and I'd get stuck in them, but that was patched and is now fixed. Has a little bit of problem solving in it, and your classic black or white moral choice system that basically forces you to go full one way or the other. The dialogue wheel basically always tells you what is the right thing to say, and it is impossible to pick a choice that will have any real impact on the game. Picking the top left option also almost always gives you the option that will make the person you are talking to happy. In 2 it was the bottom left when talking to one or two characters, but majority top left. I can't think of anything like those two characters in 1, but there may be.
As is always, the stories are good, if a bit cliched, and the dialogue is brilliant in both. Dragon Age takes a bit of a better system to run than ME, especially in the areas with large fights against 15 or more enemies, but both aren't too system intensive. As is obvious, Mass Effect is Space and Dragon Age is High Fantasy.
