Hmm like which problems are common in games like skyrim? Gothic and Risen are both open world, Smooth water edges have been FO3 (an open world game made by Bethesda), Oblivion had had nice looking actor shadows (an open world game made by Bethesda).
.......Older game engines are almost always worse than the newer ones. Very evident in the comparisons you drew. How you even compared those games to skyrim is far out of my realm of imagination.
Gothic and Risen have complete crap graphics. Seems like you thought this was a numbers game and just threw them out there.
Oblivion? Skyrims predecessor? "Nice-looking" shadows don't make up for its other poor graphical qualities. This is practically skyrims old husk... simply void comparison.
FO3... FO3? Good water edges. But, graphically average rocks, weapons, characters, walls, and uh pretty much everything else. Definitely graphically worse game than skyrim, period.
The majority of resources simply cannot be spent on graphical overhaul in big games like skyrim.
Unless you play in 480p skyrim has completely reasonable graphics.