Guild Wars 2. Free to play, they do have micro transactions, but nothing that forces you to buy it. But allows them to provide a constant support, updates and patches as well as new content. You lose nothing by not buying their 'gems'. Gives you access to more bank space, or special fun items, special collectibles, but nothing that's a must. PLUS, and this is a first that i've seen, if you deem you do want to get extra bank space and thus buy gems, they have an IN GAME currency exchange, allowing you to turn your hard earned Gold into Gems. Again, not forcing you to buy with real money.
The game involves a long engaging story, fun dungeons (some more fun then others, but their new one Fractals of the Mist are REALLY great), PVP (or World Vs World Vs World). There's a lot of areas to explore, sight seeing, Map completion bonuses, and even special Jump Puzzles. Some are hard, but challenging and keep you entertained.
Worth looking into. I'm loving it so far! I'm on Jade Quarry server if anyone else plays.