Oh there are tons of games out there - many that are free-to-play. I've tried many of them and - sadly - most are the 'same-old-same-old' WoW clones.
When it comes to recommending the best ones, the list becomes noticeably shorter.
TERA RISING (I recommend the US version over the European version) is very similar to Aion, with wonderfully detailed characters and a gorgeous world. It possibly the best-looking game out there. However, it's a bit difficult to get used to as you use mouse AND number keys for spells/attacks and WASD for movement. This means you really need three hands to play with their set up, unless you're really good at finding all the keys without looking. I got round it by assigning the 'Run' hey to a button on the side of my mouse. Essentially this is a better looking version of WoW with some interesting touches.
STAR WARS: THE OLD REPUBLIC. Doesn't matter if you love or loathe Star Wars, this is a great game. Again, it's very much a WoW clone, but the twists here are companions and class storylines. It also includes an interesting (though tough) space combat system. The only downside of SWTOR is that you really need to be willing to pay a monthly sub to get the best out of it.
GUILD WARS 2. The best MMO on the market right now, as it dispenses with all of the things that makes WoW and it's clones so annoying. No kill stealing, no XP or loot stealing. Everyone who takes part in a kill gets XP (and you don't even have to be grouped with others for that to happen) and their own loot. Level scaling means you can go back to low level areas and still face a challenge, plus you get XP and loot in line with your actual level. Your personal story depends on your race and choices you make during character creation. Later story choices depend on which of three orders you choose to join and there are multiple story direction choices. Total freedom to explore in any direction you want, allowing you to remain in low to medium areas, or head into really challenging areas. Freedom to use different weapon combinations that have different attacks for different classes. Great crafting system that produces things you can actually use from an early level. No need to buy anything with real money to gain a big advantage over others (apart from inventory/bank expansions - if you want them) as all bought items are essentially cosmetic. The only downside is this is NOT a free game - you have to buy the core game - but you have the game there are NO monthly fees.