The Pokemon games have always been too easy for me personally, so I enjoy setting myself an additional challenge. Nuzlockes also give you an additional attachment to your party, which adds an element of emotion to the game. I always play through the games normally at first so I can take the best advantage of the new environment though.
I've recently started playing through the Crash Bandicoot series again. Before, I always used to feel Warped was the best game in the series, but after replaying them all, I have to conclude that Crash 2 is superior. The jetski and motorcycle levels in Warped are hell, and they happen to be the most common levels, appearing 4 times each.
Crash Team Racing is a very solid racer though. Maybe not quite on the level as Mario Kart 64, but a hundred times better than the fecal matter that is Sonic R.