Happy birthday OP !
For Xbox Series owners : the whole saga is available in BC compat and can be bought digitally too, if you are like me and played them at release for each systems there were on, there's a huge reason to replay them all now as they all got significantly improved with higher resolution and smooth frame rate that really transform the experience, no more freeze frames when triggering alerts or caution for the enemies, no drops in framerate and really fast load times, better yet the image quality is now tripled on certain titles (conviction was awfull at 576p now it is 1700p)
the first two Splinter Cells are in 4/3 aspect ratio with huge black borders but runs flawlessly, you got the DLC included for the original with 3 added missions !
The biggest changes are for Double Agent (Xbox 360 version) the game was atrocious performance wise, screen tearing everywhere, sub par frame rate, now it has stable 30 FPS and it is a game changer, playing the cruise boat level with the giant swimming pool and fountains on the main deck is now possible without looking at slide show!
As For the games, they are all worth playing in my opinion, the best are Chaos Theory / Blacklist, the worst are Convictions and the PSP ports, 3DS etc
I remember the first Splinter Cell commercial on TV, I was blown away at the details of Sam hair when in night vision when the camera is over the shoulder haha.