I'll just list some games I have played and my impressions of them. In no particular order.
TERA (Free):
This game is a great mindless grind game. If you're bored and want to kill some weekend time, here is a great game for doing nothing rewarding or intellectually stimulating. I like the dynamic combat system. It's not tab-target based. You actually have to dodge the monsters' attacks or else you die. I like that. That makes it really fun. Healing in this game absolutely sucks, though, because a lot of the heals are skill-shots. So if you like to play a healer, this game will teach you how to hate playing a healer. Just picture being in a boss fight wherein the boss just did a huge aoe skill on your entire team and you have to top everyone's hp up super quickly or else you're all going to wipe, but everyone is moving around all over the place and you have to LAND SKILL SHOTS ON THEM while they're running from the boss and cavorting all over the damn screen. While also trying not to die yourself.
Portal/Portal 2 (Not Free):
I don't really view stand-alone games like this as "video games." Video games to me are MMOs. Portal is not an MMO. Portal is, however, a damn good game. So intellectually stimulating, as well the story line is cool as fuck. Really loved Portal 2. The atmosphere of the game is seriously stunning to me. Love it so much. I fell in love with the chamber designs and overall mood of the game while playing it. Love it so much. Definitely a world you can get lost in.
League of Legends (Free):
I have a love/hate with LoL. If you just play it casually, you will probably like it. Especially if you play it with friends. Friends are key in LoL. You can't play it solo and expect to enjoy it. Unless you're one of those robots who ends up becoming pro at the game by spamming solo queue. It's very, very team-reliant, which is why I suggest friends. And Skype. It can be very fun to play with friends, even if you are losing. Which you should be doing about half the time, as the match maker system auto-corrects after every game played, always shooting for a 50% win/loss rate.
Trove (Free):
I really, really like this game. I wish I could tell you why. It's something about how simple it is combined with how immersive it is. It's similar to Minecraft and similar to League of Legends. I'll explain. The world is made up of blocks like in Minecraft, but you have different classes you can play as, like in League of Legends. And you can swap classes at any time. And you level up those classes to a max level, at which point you can not level up that class any more, but you can of course still play the class. And ya there are many classes to choose from. The more you play, the more reward points you earn that will let you unlock more classes--just like in LoL. But Trove is an MMO, not a MMOBA like LoL. Trove has a nice community-based playstyle. . . by that I mean that people group up tons in this game because there is no incentive to play solo. And tons of incentive to group up. And so you'll never be without people to play with. So I really love that. And there's no party system--to receive group rewards, you need only to be near other players. So easy. It's really great. I would recommend downloading this game and just trying it if you're interested. It's on Steam. Free. The gear in the game is very obtainable by everyone. It drops from monsters that you can solo. But grouping obviously makes this easier. And there's no grinding for hours and hours to get a particular drop because the game's crafting system lets you customize any weapon you get into the exact weapon you want to have. It's seriously great. Can't say enough good things about it. Seriously, ask me about it if you're curious.
Rift (Free):
This game is not much different from other MMOs. This game looks similar to WoW, but the graphics of Rift are much, much better. I did enjoy Rift. Probably because I enjoy MMOs, and Rift is an MMO. So . . . go figure that I liked it. But to be frank, it really doesn't bring anything new or special to the MMO genre. It lets you play as every class on the same character--simply open up the menu interface in-game and switch your class in seconds. Really nice feature. So that's different from other MMOs. Similar to Archeage in that respect, though. If you have any specific questions about this game, I'd be happy to answer. But as of right now, I'm struggling to come up with things to say. I played til max level twice and even stuck around a few months after that. Healing in this game is extremely fun. One of my favourite games for healing hands-down.
Archeage (Free):
I couldn't get into this game at all. Overhyped, in my opinion. It's sort of one of those mindless grind games that tries to be super immersive. And maybe it is super immersive for some people. For me personally it just seemed tedious as hell.
Runescape Members (Not Free):
RuneScape offers a feature (well, many features actually) that other games do not have. For me, this feature is
arbitrage. I love arbitrage. Arbitrage keeps me playing the game because I love predicting the markets and making bank off being right. This feature is obviously optional, though, and you have no need to indulge in arbitrage to be financially successful in the game. Or even to enjoy the game. But it's definitely what I enjoy most about the game that many other games never offer at all. Quite sad, really. Many aspects of the game are AFKable, so you can have RuneScape running in the background while you play another game, such as Trove, in the foreground. In this way, I kind of view RuneScape as like a very sophisticated chat room.