I've pretty much hated each splinter cell made, and I've bought the first two. They were so much trial and error and got pretty old after awhile, and I didn't like the gameplay much anyway; it seemed like you had to do stuff a certain way in order to succeed.
The Metal Gear games are a pretty old franchise that spanned before ps1. The games possibily did borrow from others but on the whole the franchise always seems to prove its uniqueness.