TBH, for me the only online game that still keeps me interested for long times is Guild Wars 2. Get it, it's free to play after you buy the game. You don't need to spend one dollar and are basically ready once you get exotics.
I played ESO till silver cauldron and stopped as the grind to play the other factions is too big and unenjoyable. In Guild Wars there's no really a grind as exotics are all you need if you aren't competitive in PVE (Dungeon Speed runs, even then the 5% stat bonus is no really that relevant. And fractals you can do with exotics till scale 19.).
Nonetheless ESO is a good game. I can say that you will surely enjoy yourself until veteran levels. It is no ES game, though, imo. Being really honest with yourself a lot of people add mods to the ES games and that means, the original is lacking certain aspects. And that you see in ESO, too. Too much customisation means bad balance overall. There is a reason WoW & SWToR for example streamlined their classes abilities to achieve greater balance. Rift made hybrids basically non existant. GW2 also has balance issues but the balance from release to now is so better. Only small things cause issues currently. And those are for example the added cele stat in PvP.
ESO PvE is very fun, though. Once I got the proper build. I played Templar Two hander and it was sooo bad. Then switched to DK and mauled everything in my way. Not funny at all. Once I got a better build and respecced my templar it was better. Still the DK was superior. Anyway try it out. You won't be disappointed if you don't see ESO as a Skyrim Online.
Besided taht I can attest that Rift is very fun. It is older, no good graphics but a very fun game. You should try it out. Doesn't cost a dime. Same for EQ2. An astoundingly good game. I had a lot of fun for month playing it.