I've already recommended Fallout 3 as a Game for Christmas, because a player needs time and a festive setting to fully take in and comprehend the world of Fallout 3, a world set 200 years after a nuclear exchange obliterated civilization.
Why is Fallout 3 the best role playing game of the year? Mainly because it pushes the boundaries. The title, made by Bethesda, which also delivered the games of the Elder Scrolls series, together with the very divisive Oblivion that arrived in 2007, managed to create a deep, engaging and complex experience, allowing players to create complex narratives around their actions while also giving them the freedom to roam around a beautifully constructed world.
The SPECIAL system gives the flexibility to create any type of character you like. I played first as an Energy Weapons specialist who took out enemies with plasma and laser rifles while having a knack for hacking computer terminals; in my second round, playthrough is still on going and has my character as a close quarters brawler, focusing on melee attacks while being very skilled in medicine and lockpicking. This kind of freedom is the mark of a true RPG offering a lot of replay value.
Unfortunately, the game does not provide as much incentive for multiple playthroughs with its take on morality. The overall story forces you to be good and even if you proceed to take out a lot of characters, being evil does not seem satisfying.
But the locations created by Bethesda, from downtown DC to army bases and Enclave headquarters hidden deep inside mountains, are well put together, with an eye for detail, and the VATS combat system is a good adaptation to real time of the turn based combat of the first two releases. The title is set to receive DLC in early 2009; thus, gamers will have even more reasons to play it.
Honorable mentions as far as RPGs go are The Witcher, which is more by the numbers but is really enjoyable, especially in its newest incarnation as the Enhanced Edition, and King's Bounty pairing excellent tactical turn based combat with a weird and humorous game world.