I got around 800hours or so in D3 and it is basically a love/hate relationship. I don't play it now, but I know I'll come back at some time. The best part for me is going through Act 1 with a new character because that act is just the most nostalgic for me. Always fun to start from scratch and get that first legendary drop, though unfortunately a lot of the time it is the Leoric Crown for me. Doing Act 1 on Torment 1 as a fresh character is also quite fun, since most things can one-shot you, you have to upgrade your gear fast to do a little more dmg and kite them mobs a lot of the time.
I have booted up GW2 again lately. Also, a game you can play solo, and it got some very cool jumping puzzles which I especially like doing. The Mad King Clock Tower is my all-time favorite:
I was a guild for roughly a year or so and the World PvP and some of the PvE dungeons are not too shabby, but I have always liked to just explore the game solo, especially since most of the quests you can do by yourself or you can join a random group doing the quest (finishes them faster that way) but still being alone doing it if that makes sense. It actually does not look too bad either for an old game. Can't say my beginner armor is great looking (80's metal band look), but it is what it is:
what the best games MMO RPG?