Good Things:
1) Origins
2) Companions and the relationship system (though gifting makes it a tad bit "easy" to keep everyone happy)
3) Strong npc cast (especially Loghain)
4) Awesome background and tone (not as oppressively hopeless as ASOIAF, but still dark)
5) Strategic Combat that allows for multiple ways to victory
6) Main Story Quests are all good (some better than others)
7) Interesting Moral Dilemnas (Is Loghain right or wrong? Mages or Templars? Kill or save Connor? Which dwarf king to choose?)
8) Awakening was a neat expansion pack (you get to run your own arling, act as commander, and determine outcome of darkspawn civil war)
Missed Opportunities (aka, the kind of bad stuff):
1) Orzammar is cheap because there's no way of knowing that Harrowmont will be a bad king without meta-knowledge. Vice versa with Bhelen being the "right choice" without aforesaid meta-knowledge
a) Not being able to become ruler as dwarf commoner/noble despite having two loopholes to do so (Provings and Paragon endorsement) Yes, you are declared a Paragon, but why not eat both the cookie and the cake when you clearly have enough money for both?
You can't spare the Anvil without siding with crazy Branka (I get the point, but considering the number of times that persuasion is employed, it makes no sense that we can't convince Cariden that the Anvil is needed. Yet, we can convince crazy Branka that the anvil must be destroyed. It just seems uneven for no real reason than "drama")
2) Landsmeet is tedious and is impossible to fail (Plus, does the monarch have to be Alistair and Anora? How about making Teagan king? Cousland as sole ruler? Side with Loghain? (As crazy as it sounds))
3) Loghain recruitment dilemna is forced and contrived (Why loghain? Why doesn't Riorden tell Alistair and the Warden about the Archdemon thing? Why not put someone else through the joining like one of the many knights in the capital?)
4) Rogue/Mage companion options are limited (it's somewhat easy to be stuck with one or no rogue/mage characters (like if you kill Wynne or Zevran for instance))
a) Leske or Shianni would've been neat full-rogue companions
Jowan was actually planned as a full-companion, but scrapped for budget reasons
5) WOG retcons that don't make sense
a) Loghain not being as involved with Howe as the game suggests (which makes Loghain seem like an idiot for working with him)
Templars actually do need lyrium (Hawke, Warden and Alistair were in-game proof to the contrary and Alistair (who was trained as a templer) stated that the lyrium thing was more of a control-device by the Chantry