Skyrim probably has the most to offer as far as longevity. There is so much you can do in that game that it's easy to pick up and just play for a short time and feel that you've accomplished something. Just walking around and exploring is one of my favorite things to do in that game because there's always something interesting over the next hill. The game is really nuanced and detailed, much more so than oblivion. I've probably sunk a good 65 hours into the game and I'm far from experiencing all of the content. Every time I talk to someone in a town they have something new that they want me to do. I understand there is also a dynamic quest engine that creates quests for you if you ever exhaust the majority of the content..which means that the game literally never ends.

I haven't played Ultimate Tenkaichi, but the Raging Blast games are a disappointment compared to Tenkaichi 2 and 3 for PS2/Wii. Although the graphics are improved the controls aren't as intuitive and the combat isn't quite as fleshed out. I'd like to try Ultimate Tenkaichi though, looks pretty promising.

GTA4 is a good game, definitely one of the must haves for this generation of games imo. But the plot and characters are missing that trademark silliness that the previous GTA games have. It's a well designed game and the protagonist is the most interesting of the lot but the main mission line gets a bit boring after a while to be entirely honest.

The games you listed are definitely good games in their own right but Skyrim offers the most in playability and longevity. It's probably one of the most captivating and immersive games I've ever played.