No matter what the Elder scrolls series will always be #1 RPG for probably the century. No other game can compete in the long run. MW1, 2, and 3 only last so long, but with elder scrolls you will never go bored. <--- fact
i got bored with Oblivion because of the quest markers, the lack of exploration there was compared to Morrowind, and the fact that people would tell you that a ruin was here on the map but wouldn't be bothered to tell you what road and so on to follow to get there. (resulting in my rock climbing skill being mastered very quickly because I'd go over a mountain rather than around it. oh wait...)
I haven't got bored with Morrowind.
It depends whether elder scrolls are following the same trend as COD. Modern Warfare 2 takes more skill than Oblivion because it requires greater proficiency to be great at the game than Oblivion did. Cod requires amazing reflexes. Oblivion's quests are supposed to require problem solving and investigation, not necessarily particularly good combat skill, and thanks to the quest marker system, for me Oblivion had no challenge. I've said this on this site before, and I'll say it again, a trained monkey could play Oblivion and be as good as the devs. A trained monkey couldn't be as good at Modern Warfare 2 as the developers and gamers with reflexes of a fighter pilot. If Skyrim continues the same dumbing down trend as Oblivion, then I'll go for Modern Warfare 3 every day of the week, because I get what I pay for.
Just to be clear, I would much prefer to play a game that required 'smarts' over reflexes, because my reflexes are pathetic. I'd prefer to buy Skyrim, but only if I can play and compete at being the "best" at it with my mates, as opposed to getting the urge to eat a banana and climb trees every time I play. Being the "best at it" doesn't necessarily mean having a character who can kill a dragon faster, rob a house quicker and so on, but being able to complete that quest that my mate got stuck on because he couldn't follow the in-game clues and work out what to do.
The fact is, at my high school, Oblivion had a reputation of being a nerdy, pointless game. Modern Warfare 2 is the game that was always more widely talked about. There has to be some competitive nature to the game, as opposed to the developers baby sitting the player from start to finish, for the game to be successful. You have to be the best in the world at that game knowing that you could have failed, not knowing that you are sharing the title with every other player.
Call of Duty will have more inter-player competition. The guns and maps are just aesthetic little details, but honestly at the end of the day, the aesthetics don't make a game better or worse. Look at Crysis. It has amazing graphics and so on, but it didn't sell as many units as Modern Warfare