I played the collection last spring. The first one is still one of the best 3D platformers ever made.
The 2nd and 3rd one are completely different with a lot more emphasis on shooting and driving/flying. They are a lot harder too, sometimes to the point of frustration. However this time I stuck with them and finished both. It was definitely worth it in the end.
The collection is worth it's admission price for the first game alone. The other two are a bonus.