I'm playing WoW and CoH along with SWG. I guess the key is to find out what about SWG you don't like. Honestly, the changes to SWG made it more like the other MMORPG's out there, so you may not enjoy any of them.
CoH is great for pick up and play. No crafting, no real items, just quests and arresting of thugs.
WoW is stellar. You can solo, though if you do, you'll likely feel like you're just playing a limited RPG. But I do hear the end game is weak, though Battlegrounds comes out soon, and may change that.
Personally, I thought MxO was so-so. I was in beta for a couple months, and it seemed like a weaker version of CoH. Some amazing potential, but missing some key elements.
Same for Guild Wars - it was fun, but for fantasy based gaming, WoW was superior for me. I also don't love the PvP, so Guild Wars' main appeal wasn't there for me. I did like the system - mixing the classes, only having 8 skills. And the no monthly fee thing was a great marketing idea.
DnD online looks promising, but that will be a while. Auto Assault is looking good from the beta stuff I've seen, but may lack staying power.
Course, I like SWG still, so take all my comments with a grain of salt.
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Jester, Lvl 6 MNK, Kujata
Badjuju, Lvl 38 Frost Mage, Moonrunner
Plainsrunner, Lvl 25 Feral Druid, Moonrunner
Dedbob, Lvl 18 Warrior, Moonrunner
Orthros, Lvl 12 Paladin, Smolderthorn
Shyy'rissk, the Angry Wookiee, Flurry