@CA Without a doubt, D&D is by far and away the best known RPG system out there. That doesn't mean it's the best though.
World of Darkness consists of quite a few different lines. nWoD (New World of Darkness) is a better system overall in terms of it's mechanics. Vampire the Masquerade is part of the classic World of Darkness.
nWoD's core lines are the following:
Mage: the Awakening, where your character has come by the ability to shape the universe itself, but you're also targetted by abyssal creatures who see you as an easy portal to the mortal realm. Mage's theme is that of hubris.
In Vampire: The Requiem, your character is a vampire in a world of humans. Stepping out into the sunlight is certain deaths. It's a very political style of game, with lots of backstabbing and backroom maneuvering. Vampire's theme is trust.
Then there's Werewolf: The Forsaken, where your character is a werewolf, trying to control the primal nature in you, and maybe failing. It's a very savage game, built around trying to keep yourself alive as you try to figure out what's wrong with you. Werewolf's theme is that of savagery.
nWoD also has a number of non-core lines. They're as follows:
Promethean: the Created. In this game you are created in a style similar to that of Frankenstein, then given life. You've been made with a number of other people, and so you cling to those people. Promethean's theme is that of identity.
Changeling: the Lost. In CtL, you are a human who has escaped enslavement by one of the faerie folk- to the point where you look barely human- completely replaced by something else, that may not even realize what they are. If you play changeling, you're looking both at the past- where the Fae are hunting you- and to the future, where you have to death with the pain of loss, and the bittersweet nature of human existance.
Hunter: the Vigil is a game where the characters are monster hunters, tracking down things that go bump in the night, and making sure they don't threaten Sleeper (people who don't comprehend the World of Darkness) existance. It plays off of the tropes of Men in Black. You don't hunt down everything, just the ones who have gone out of control. The biggest theme of Hunter is that of protection. Both of yourself, but also of those that you love.
There's a couple others that are coming out soon, so we'll have to see what they're like.
With WoD out of the way, I'll cover the fun paranoia next.
Paranoia is a fun little game that's great to run in a one-shot. In Paranoia, players are Troubleshooters for the schizophrenic communistphobic Friend Computer, (Hello, Friend Computer). Troubleshooters have to fulfill the goals set for them by Friend Computer, but also those that are given to them by the secret societies that they follow. If they conflict, blame it on one of the other troubleshooters. It's a fast-paced, sometimes over the top game where the players not only are paranoid what the GM is going to do next, but also what the person right beside them might do.
Iron Kingdoms is an ironpunk fantasy game, originally done in the d20 system, but recently updated to it's own system. You play a group of characters in the Iron Kingdoms (the setting for the Warmachine universe), typically mercenaries, though you can work with other things as well. You can go from a mage to a mechanic, to an investigator. It's combat is tight, there really isn't any caster supremacy, and the base setting is awesome. I'm loving playing it right now.
Honestly, I think that the biggest gripe that I have with D&D is that you're limited to the style of character you can build, otherwise you're incredibly sub-optimal and not really all that badass. 4e lessened this a bit, with the fact that the game tells you straight up what's needed to build a character the right way, but at the same time, characters are still limited. It has to do with the Attribute-Class combination. But that's a whole bugbear that deserves it's own thread somewhere else.
