There were some things which i didn't like in many of its games especially in Oblivion and Skyrim. One of the worst things for me is level/item scaling as i believe that with proper implementation they could still achieve the freedom and challenge they have now. They also do have some flaws in dialogs, some imbalance in crafting skills, they could use more scripts to help immersion, they should not oversimply things and could have a more sophisticated combat system.
However even with these flaws they are simply outstanding. Only a handful of companies create this great genre of games ("sandbox"/open world rpgs) and Bethesda's are, by a large margin, the best. If there was no Bethesda around this genre would practically have eclipsed. Also nothing is perfect, especially in every person's eyes at the same time.
I did my share of criticism and will continue doing it - unlike in other games - and the reason for this is that i love them enough, to bother and spend hours here posting, or don't want them changed to something else. I also hope both the good words and the criticism reach the developers ears and that they bring their games closer to perfection while not changing what they are.
Also, as a pc user, i am extremely grateful for releasing a construction kit and making the game mod friendly, to allow modders to make further adjustments to satisfy everyone's needs. Not many companies do that.
(Hurry up and release it!)
Also it would be great if users did more constructive criticism on this forum (already most of the posts are fairly constructive, unlike when new vegas was released) and it would also be great, if another part of the users did not recieve this criticism as hate or plain complaining and tried to see one's views spherically.