1) MGS3 - best bosses since 1, best story of them all. hands down the series' pinnacle.
2) MGS1 - the innovator that started it all, still has some of the best bosses in gaming.
3) MGS2 - weaker bosses, but i dug what kojima was going for here - great level layout at parts, and the crazy existential plot was fun for me too.
4) MGS5/PW - this was great for a PSP game (still havnet touched the HD one yet, but i will!), my only real gripe is that much of the plot lies in the shadow of 3's greatness.
5) MGS4 - Had some moments, but weighed itself down with poor editing/bad fanfic story and convolution.
6) MGSPO - Fun for what it was (and i really dug ashley wood's art once it was animated), but EmCee here @ GAF pointed out the revisionist story with zero and that kinda messed me up.
glad i didn't have to rate Ghost Babel (never played it) or the MSX classics, that'dve been tougher!