Xenoblade Chronicles, for the Wii. The game is a hidden gem, but since it's so long not many people run it, unfortunately.
At your suggestion, I checked, just to see how long "long" is... oof. The shortest category still over three hours! I think I recognize you from the Introductions thread - is that what you're going to run? Look forward to seeing your submissions!
I'm adding Clash Royale to my list. Even though it's just a mobile game, it's extremely fun to run as you need skill, luck and strategy. In case you're interested: http://www.speedrun.com/Clash_Royale
Currently the only runner, would like to have some competition.
I'll toss in the game I'm running, On the Rain-Slick Precipice of Darkness 3. Pretty easy game to learn and one that only has a couple of runners atm, myself and ChurchnSarge.
Jazz Jackrabbit 2! Fast paced and not too hard/easy to pick up with some interesting quirks/glitches. Although I haven't submitted any runs for it yet, I will soon. In fact, there's lots of literally free WRs, especially in The Secret Files! The only active runner right now is BinaryBlob.
Here's what I consider the best run so far:
Unfortunately, the game is long out of print and it seems Epic has no intention of rereleasing it, so you will probably need to "sin".
And there's the other game I run, but it has a lot more attention - Freedom Planet. It may not be easy, but it's a blast when you go fast - you have to work to retain momentum. You may initially think "OMG wat a Sonic rip off!" but there is actual combat (no jumping on enemies, you got to use your attacks), no enemy collision damage, and a lot more interesting tech, especially with Lilac. Each character feels distinct from each other in playstyles.
It's actually relatively popular as a speedgame, but not among the famously ran. You can find it on GoG, Steam, or the Wii U eshop. Be warned though, it is rather well optimised, so only run this if you have fun. Also, uh....theres a few ridiculous tricks...and the occasional dropped input. Every now and then, you'll also get an unintended glitch.