Even in Oblivion, which was pretty colorful and light, was still striving for realism. Failing perhaps, but striving nonetheless.
Oblivion looks slightly cartoonish now, but only in retrospect. Those who were around when this screenshot was released (http://pcmedia.ign.com/pc/image/article/568/568154/the-elder-scrolls-iv-oblivion-20041122022247733.jpg), will remember how we were all impressed by the lush forests and the normal maps, the impressive draw distance and later the dynamic shadows (which ended up being removed). The first image of Oblivion had us all drooling over how much of an improvement it was over Morrowind's blocky characters.
The notion that it looks too colorful and light hearted came later. It was very positively reviewed for its graphics, but later was somewhat discredited, mostly due to the generic medieval themes, poor animations and unfortunate facegen features. By then, we were being treated with progressively better looking games, all which made better use of Xbox's rendering capabilities. Vanilla Oblivion didn't age so well.
TES games always had a distinctive visual appeal, it wasn't only the sandbox aspect that pushed sales. Daggerfall was released in the year of Quake and Tomb Raider, so it wasn't cutting-edge. But it was still attractive next to Duke Nukem 3d and Diablo, also released in the same period (and what an year!)
They may not have been revolutionary, but they have never looked bland or dated when they were released. TESO's environents look attractive, but then again so does Lord of the Rings Online, which is over 5 years old. Age of Conan has similar looking environments, even though it's 4 years old. Both games looked fantastic when they were announced and required steep hardware to look their best. But not The Elder Scrolls Online. They're placing all their bets on accessibility, even though the Old Republic proved earlier this year that just because everyone can play, doesn't mean everyone will play.
I disagree TESO looks like Wow. But they're certainly aiming to copy Blizzard's sucess and designing a game that is neither innovative or intriguing. It's been repeated in many interviews that their objective is to create a "fun" game, and while it does sound fairly obvious that any game should be fun, it also reveals much about their design philosophy. It lacks enough visual appeal to stand out (especially if new consoles show up in 2013) and pleasing hardcoe fans is not too high on their priorities. They're going for the casual player, whose familiarity with the Elder Scrolls franchise extends as far back as last year's Skyrim and hopefully Oblivion. Except casual players have very low adherence rates and after the first few months, designers are fighting a hopeless battle against time in order to keep subscriptions from dropping.
The producers will then rush to develop endgame content and hardcoe features that were left out from the casual friendly release in order to try and establish a hardcoe base. But then it will be too late. Server merges and an year later, the game settles down as a moderate sucess, just enough to keep the project funded. An year later, it's shut down to open room for new projects, it's switched to free-to-play or the servers are merged for a "healthy" population and a passable profit margin. But all of those outcomes are far from the original high goals of being the next big hit.
We've all seen this countless times before and I guess it proves that only a handful designers will have the balls to push forward the genre, and from those, even fewer will have enough influence to persuade the industry to support unproven formulas.