How do you Build Six Rollercoasters right next to eachother? I saw it on gamewinners, but it doesn't work in the real game. Also, if possible, how successful do these rollercoasters become?

You have to adjust the platform stations so you can fit an entrance, and exit and make sure the track is a complete circuit on each one. It's not impossible, it just takes some thinking. And the rollercoasters usually have very high excitement ratings around 10 or 11 if built right.

It is, but you have to make sure that they aren't all going the same way. Then the roller coaster on the inside is smaller than the rest.

Have all the stations different lengths, starting at different places, even doing that its very very difficult

First one has a station two long. Second one has a station right next to it, four long. Like this:

-----------------------------------[Entrance]-------[Exit]
--[Entrance]-------[Exit]-------[Station Block][Station Block]
[Station Block][Station Block][Station Block][Station Block]


Etc....