go ahead and download the creation kit and look at the variety of kits available.
If you look in creation kit you can see that most of the building blocks are used 500+ times. Of course any game will re-use set peaces a lot, but the problem with Gamebryo games is they relay on the too much. Every dungeon might have a different layout, but most of them look and feel the same.
It's basically comes down to openness vs variety. A linear FPS doesn't have much room too explore, but can have a ton of variety. Skyrim on the other hand has a large world to explore, but in order to meet size and practicability limits it has to sacrifice some variety. I'm saying that I would like some more variety in the main quest, even if it means the world would have to be slightly smaller.