Middle of the road (you might say "standard") films would be Provia and E100G. They give the best balance of features in most situations.
A subdued film (less contrast and saturation) would be Astia. It can help combat high contrast, but can also look like mud if shot in unsuitable lighting. And it isn't a good choice if you want the colors to really pop.
The snappier films are E100VS, and all three varieties of Velvia.
Velvia 50 and 100 are both very contrasty and saturated. The main difference is in color balance; the 50 is warmer. 100F is the least snappy of the Velvias, but definitely gives more saturation than Provia. It is also not warm like the 50.
So, you only have six choices, three of which are varieties of Velvia.
I'd say that if you are in doubt about which film to use, just go for E100G or Provia.