How about an indoor, high banked concrete tri-oval. The track should be about 250' long with progressive banking and 3 different radius corners. Also heating coils should be under the track for the most consistent track surface possible.
Now back to reality! What kind of track were you thinking about? I'll assume flat carpet oval. When it comes to flat carpet I prefer a bigger track, maybe 175 to 180', with somewhat wide corners. If you ever raced at Trackside in Brookfield, WI, I liked that track layout. Bigger tracks are easier for less expereinced guys to get around and they allow more passing opportunities for the experienced guys to actually race each other cleanly. All the flat carpet tracks nowadays are basically the same thing. What would be really run is running a a true tri-oval or having corners with significantly different radii. That would really show who can setup a car and drive. Unfortunately it isn't too space effificient in buildings.
Now if you are talking about any type of track then I think flat ashphalt "parking lot" type tracks are the most fun. Unfortunately outside of Florida there is not much of this type of racing anymore.
If you're talking cap tire tracks it is very dependent on the surface whether the track will be fun. If you tear tires every run the track won't be fun. If the track is too much of a paper clip shape guys will be trashing their cars on the outside wall and it won't be fun. Also a grass infield cuts down the fun factor by 50%. Cap tire racing on the right track is awesome and on a bad track it sucks.