Well, I wouldn't say best, but the most common. WoW is a bit old, granted some mechanics will be timeless, but best comparison would probably be the more recent MMO's to date, as they are better representations of what NOT to do or what TO DO. WoW is just the most well known due to its massive player base.
You can't deny it's the best at making money, or like you said, the best in terms of # of players - isn't that something TESO should be shooting for? Being successful? Not necessarily to the extent of WoW, and I know plenty want it to be a niche game. That's why I said best and worst, because of the reasons you listed, and the ones I did. In actual gameplay, graphics etc. they shouldn't be compared at all, in business, in content updates? You bet.
another example of a terrible game to me is all the games that can be beat in a day like assassins creed and the like.
Why are you interested in TESO then? TES games fall into that category. It doesn't take a day to beat the main story of skyrim, morrowind, or oblivion, if that's how you define "beat". If you mean thoroughly exploring content, then no. I'm playing FFXIII right now, and it's linear and all about the story, and haven't beaten it in a day. I've been playing it nonstop for two days and am only a little bit over halfway done - it's already worth my purchase 16 hours into it and I'm sure I'll replay it many times. It can't compare to TES games in how much time they can soak up, but that doesn't make the quality of the content bad.