Reading through the posts I get the feeling that the fans have hyped the movie up just like Khan is hyped up. It's true Khan doesn't really do much aside from being a standard bad guy with a ship. He tortures some crew members, kills some civilians, manages to get the jump of the ENT while it's shields down and survive to the end just to lose to the heroes. In that respect Khan is comparable to the Borg in FC, Shinzon in NEM, and Nero in XI. Although no one shows the same adoration for these villains even though in a measurable sense these villains were much more successful. I get the sense Trek fans want Khan to be Trek's Darth Vader and Khan really doesn't have the star power for the role.
The story behind the Genesis project is intriguing but it's not very developed even though it was talked about a lot. Khan wants it but never states why. It's the audience and the fans who have to connect the dots for his motivations. More evidence of the fans filling in the blanks for Khan's character and actions.
TSFS has more of an adventure behind it. Stealing the ENT, assaulting Star Fleet personnel, fighting Klingons, escaping an exploding planet. However Spock's revival, and David's death I think hurt TSFS because they were so important to the story of TWOK.