metal gear solid is a tactical-action-adventure-shooting game, One of the best games ever. You can even check all the game reviews! Metal Gear Rising (or the one with Raiden) was a different kind of game since it was published by Platinum Games who created the game "Bayonetta". MGS always has a good story to tell and had lots of easter eggs and gun customization. The games pre- MGS4 is just mostly for the single-player so of course its limited but MGS4 there were many things to do. Can you try replaying the game in the hardest mode without killing anyone or getting spotted? You can play MGO which stands for Metal Gear online which was the best kind of online multiplayer I've ever played. Im sure Metal Gear Solid: Phantom Pain will be the best game of 2015 with over the top improvements since MGS4. I'd like to talk about it more but it'd be too long and I'd be wasting my time when you can experience this yourselves.
TL;DR
Metal Gear Solid series is way better than Assassins Creed(My Opinion)
I didnt like Metal Gear Solid Rising because its different but I did like it because it was RAIDEN and story fits.
If you have a ps3, buy them all if you want to experience it. Sadly, MGO is closed but will reopen on MGS5! Check out more of its MGS5 online trailer.