I'm not really a die-hard gamer, but I used to play RuneScape for about three or four years during middle school until mid-sophomore year. I've been a little bored since then, and now I'm looking for an all around great science fiction MMORPG. I did the whole fantasy/adventure shit with RuneScape, and I've always preferred science fiction as a genre. I've Googled the **** out of this topic and have never gotten anywhere other than six billion people screaming "EVE Online!" at me.
EVE Online and STar Wars Galaxies are the only sem-major MMOs in the sci.fi setting atm. But in a few years we will get Star Wars the Old Republic as well. There's also a Stargate Worlds in the making.
No, I've tried EVE online, was not impressed, and have heard plenty of bad things about SWG so haven't bothered with that one either. I just know they exist.
As for Star Trek online, that game has been rumoured cancelled and then back in production again and cancelled, so I have no idea what state it is.
Mass Effect for an MMO? Unlikely, I think BioWare is on the right path with SW the old republic, that's more or less the perfect setting for a sci-fi MMO.
I kinda fell in love with ME, for some reason. I much preferred it to the KotOR series. I suppose because I feel that in SW, if you're not a superpowered Force user, you'll never make it anywhere.