I've played most of them, from EQ up to TR

It really depends on what you want from the game.

There are free roaming MMO's, like WOW, EQ2 (that have dungeon instances/raids)

There are instanced MMO's, like Guild Wars and Dungeons and Dragons Online that have city hubs where you meet others, and then party based adventuring instances, with nothing in the way of free roaming stuff.

There are ones geared towards PvP, Guild Wars especially has a very well implemented team based arena PvP game.

Sometimes it just depends on the Lore attached to the game. The flavour if you will. Fantasy, Sci Fi. etc

My personal favourites are: EQ2 (for the lore and roleplaying), LOTRO (for the lore and roleplaying), DDO (for the co-ordinated instance dungeoneering and its twitch based combat mechanics). WoW was good as it raised the bar for many MMO's, suddenly new ones had to provide at least that many features. I enjoyed Star Wars Galaxies past and present, and I fell in love with Anarchy Online when it was released mainly down to its Sci Fi theme, the endless amount of customisation, and that it was one of the first to introduce instanced gameplay. I also love the lore/story attached to the original game, from Ragnar Tornquist (the guy who also did The Longest Journey and Dreamfall adventure games) - although his input to the game stopped after its first 4 year cycle. I enjoyed Asherons Call 2, which is now defunct, but which I feel inspired LOTRO mechanics a little. If you like harvesting and crafting then SWG and Saga of Ryzom where very good at providing a whole sub game, based on resource collection and manipulation.

Anyway, there are a lot of them about, and it usually depends on what you like, as to whether the games offer the gaming options and style of play you want.

I am looking forward to see how Age of Conan (funcom) develops and I'd like to investigate the gameplay options in Hellgate: London. Interesting times.

DDO is all about instance gaming, with a party of adventurers. If you have a decent enough group of people to play with it can be some of the best fantasy adventuring online. Its combat mechanics are based around a twitch model with DnD stats backing up the hits. So you get to swing your sword, and strafe the monsters, and actually block using your shield. Its very hands on. Unlike the majority of MMO's out there, where its tap keys to fire special attacks. DDO does follow DnD rules (well the Eberron campaign) so levelling is quite different to your average MMO. I must stress, if you play the game without a decent set of players, you'll find some pickup groups just rush instances, and don't play through it in a considered and enjoyable fashion. As with all instance games, if you have bad group members, you'll probably have a bad experience of the instance.

FFXI seemed to me to be more of same as far as MMO goes, a bit too much grind.

If you're looking for something different DDO is probably the best bet.

I'd put forward Two Worlds on the PC (but I can see thats already been recommended).

If you like the hack and slash of the action RPG, then these two have recently been released:

Chosen: Well of Souls

www.meridian4.com/games/TheChosen

A sort of Diablo Clone, with a few tweaks to make it interesting, spinning guns in with the usual western fantasy stuff, and limited use summoned minions.. basically a less complex progression path, but with more options.

or

Depths of Peril

www.depthsofperil.com

Take a fairly rough around the edges Diablo II clone, add to it some 4X ****diplomacy and conquest, and you have Depths of Peril. It's an intersting idea, taking your standard click based hack and slash action RPG, and meld it with a faction based trade and conquest ethos. Every game you play, you set the parameters for the world, the difficulty of the monsters, the number of opposing factions to your own - and then you forge a hero to go out into these areas to perform quests from the settlement hub, to level up, gains new skills, gain influence, cashand loot - as well as try to recruit others to your party and your faction (or in game its called Covenant). Once you've got a few members, and you've decorated your Covenant hut with relics and tomes of knowledge, plus placed some guards to defend the place. You can begin to start allying and ganging up on some of the other Covenants who are AI controlled factions, running similar heros and recruits around the world trying to gain the most influence and power and utterly destroy the other factions. If you are Allied with other factions just make sure when you destroy the bad guys, you have the top level of influence within your alliance, so that you can claim the win.

Despite the 1990's graphics, it can be quite involving when you begin to use your hack and slash hero, to stock up your hut based barbarian "empire". I like the scope of the game, to make a balance between the decidedly average (in terms of graphics and complexity of quests) killing and questing sprees and the empire building (basically collecting bonuses and hired hands), with the diplomacy of joining some factions together to then turn and wipe out the weaker ones. Good effort on the hybrid gaming idea.

Prince of Qin

www.strategyfirst.com/games/GameInfo.asp?sLanguageCode=EN&iGameID=37&sSection=Overview

If you want to step back in time (and presumably in price), theres Prince of Qin, which is an eastern themed Diablo Clone.

If you want some real back to basics action you could do worse than investigate some Roguelike's, theres plenty on offer here, and most are free to download and play..

Temple of Roguelikes

www.roguetemple.com

Hope that gives you some ideas.. so you can stand the wait till Mass Effect comes out :)