I was thinking about running StarTropics in the nearest future. But the game is not on the list. Is that somthing that can be changed?

If you go to the Games tab, to the right there is a Request Game button. I learned this today, that's be the solution :P

Yeah. But the game can not be anywhere els in the net.

And i saw that Darkwing Duck had posted his WR run on SDA, but im not sure if thats a leaderboard? Is there someone how could help me with this?

Ask the community if they are okay with it that the leaderboards be hosted at this site, if yes request the game and make sure the right people get mod, etc etc.