MMO like World of Warcraft? No.
A game with a lot of people? Sure.
I began playing "Rage of Bahamut" a few days ago. It's very similar to Yu-Gi-Oh but with monsters more akin to Magic! The Gathering. The graphics for this game are simple, but elegant.
The game has a few issues, particularly some lag and a few crashes; but if I had to guess it's our hardware a and less the software.
It's free and can be a game you play every hour, a couple times a day, or once a day. [I don't recommend the last.] In some ways it's alot like any other game you play with friends - it has an energy bar that will have to replenish, but fortunately it's not a long wait.
If you give it a try, play through the tutorial and when it asks you for a referral code, I would appreciate if you used mine: xqm73681 - we will both receive 100,000 rupies and a rare card.
TL;DR: "Rage of Bahamut" is a good game with a few bugs and glitches. It's very similar to Yu-Gi-Oh! If you'd like, download it and play through the tutorial and at the end use my referral code "xqm73681" and we can both receive a good boost.