They are very different effects, both in terms of difficulty and tools. Do you have any background of compositing? After Effects, Nuke etc?

Do you?
It should be obvious then what you need to do.
The hard part with this sort of thing is not the compositing or rotoscoping or even the nice motion tracking like in the X-games vid, but all the drawing involved.

If you know what you want to do then it's a matter of drawing the animation, tracking and rotoscoping your footage so the animation can fit in where it needs to, rendering out the final product.
Sounds easy right?

Here's a great (new) option for filmmakers who are interested in getting into animation.

http://www.forbes.com/sites/carolpinchefsky/2012/06/27/valves-new-animation-tool-gives-filmmakers-their-own-free-studio/

The Source Filmmaker allows for setting up lighting scenarios, importing objects and mods, and creating finished animations. It's only in beta right now, but it looks like an awesome tool -- and it's free.

http://www.sourcefilmmaker.com/

@jpbturbo I use after of like color correction and a little motion track once in awhile and use photoshop for editing photos only. I've never put the two together before. I'm pretty sure I can't create anything like the first video anytime soon, but if I could figure out how to do something like the second video that would be cool. Even if its basic stuff. I've just always wanted to be able to do something like that but have no clue how too :/

I am a professional animator and fx guy. The above X games spot is mostly 3d animation with a toon shader. Some of the effects such as the fire and some parts of the waves are 2d animated. The entire spot was motion tracked using programs like synth eyes or pf track in order to incorporate the 3d animation and 2d effects into the scenes seemlessly. As mentioned After effects or Nuke was used to composite. These spots look difficult but a small team could execute this commercial in a few weeks with good art direction and a good edit to start with.

This video is a collection of roto/paint/tracking, heavy color modification and some editing trick. It isn't so difficult to reproduce if you know the basic techniques. If you like this kind of things, the best you can do is to borrow some book about motion graphics in After Effects and see a lot of tutorials both for example and inspiration. Then you have to put a lot of creativity in it.