MMO's are appealing to most people because they give that amazing sense of accomplishment that you can share with others. In other games, your sense of accomplishment is limited to yourself and so sometimes feel less satisfying, to the point where most people now days only invest time to better themselves in games that allow them to show off to other people how good they are. Old days this was limited to console games like Mario Kart, but now with the internet, people tend to go towards more mainstream games like League, or World of Warcraft. Basically, the more people that play the game, is the more people that play the game, because thats more people that will care about your online accomplishments. Of course, this niche appeal of online games isn't for all players, but its why some games get so much bigger than others. The bigger you make the game seem, usually is the bigger the game gets. In some cases, the game doesn't even need to be that good, it can be simple, but if a lot of people play it, then a lot more people will play it to be better than the masses, thats the sense of accomplishment people want.
If you ask yourselves why MMO's after WoW all seem to 'fail', it's simply perception of how other MMO's have grown. Since WoW became the modern day mainsteam MMO, it seems like all other MMO's have been competing with it for the mainstream spot, but that's no different than trying to dethrone something like Facebook. It's self sustaining, its so popular because its so popular, people want to be good in it because everyone else plays it, and so everyone else plays it. Is it actually good? That doesn't matter anymore. It's publicity put it in first place, regardless of how good the game actually was.
So when you start asking, is ESO trying to clone WoW? Is ESO going to fail like all the other recent MMO's in the MMO saturated market? Do you actually understand what you are asking? And have these other MMO's that seem to have 'failed' actually failed? or was that all just perception.
Rift, Aion, Tera, SWTOR, GW2, these are all MMO's that released, some people thinking they would either clone WoW or kill WoW. Ultimately, none of them did either, and none of them became the new 'mainstream' mmo, so uneducated people ran around and started claiming these MMO's all failed. But did they? Log onto any game and they still have a playerbase, still have subscribers (save for Aion which is FTP). All of these games are still making money. They just aren't popular because none of them have been dubbed mainstream enough to get enough people to invest time into them for that sense of accomplishment they want to get out of video games that they are not getting IRL. They didn't fail, these games aren't bad, people are still enjoying them.
So will ESO fail? Will it become mainstream? I don't think either will happen. It won't fail, it'll be an amazing game, it'll garner a player base and hell I know I will play the [censored] out of it. Will it become mainstream is almost impossible at this point, the once small MMO community that gathered in the mainstream WoW has already fanned out among a ton of seperate MMO's, each MMO appealing to different players style of gameplay. There is no longer one 'giant MMO' that you can be good at and expect everyone to relate to you when you talk about your level 90 Night Elf. So that brings me to the next point, the MMO player base that will soon be washing up upon the shores of the public forums of ESO (Brace yourselves, they're coming).
These guys have been showing up on the forums of every new MMO, all saying the stuff 'this game needs to succede'. It'll need this feature because this MMO has it, and this one because that has it, and it'll need this and this, and these guys will never be satisfied, they'll be trying to make some magical MMO, each of them having a different idea of what ESO should and shouldn't have, and it'll all get jumbled up. These guys will be the loudest ones on these forums, they will claim to be veteran MMO players and say everything as fact 'this ESO game WILL fail if it doesn't have this, or if it does have this'. Ultimately, these guys are the bandwagon jumpers, and they are not the core audience of the game. These are the guys running around calling games WoW clones trying to find a new mainstream MMO to feel accomplished in, these guys will never be happy, and they'll never be wrong in any argument they make. You've no doubt already seen them here, or on Tera, GW2, Swtor forums, saying those games failed because -reason-. These guys have no clue what they're talking about. Please don't dumb down ESO, or cater it to any of these guys. Make ESO it's own game, give it publicity, and if it doesn't become the mainstream MMO in a saturated MMO market, don't be surprised, just make sure its a GOOD game, and people will play it.
You guys developed some amazing ES games, just trying to give you a bit of headsup on what to expect as you step into the world of MMO's, and the current state that the MMO market is in.