Metal Gear for the MSX was ok but I much prefer Metal Gear 2: Solid Snake.
Some of the best parts of Metal Gear series are the endless staircases/ladders which didnt feature in MGS2 (and to my memory 4)
Unoriginally I think Way To Fall and The Best is Yet to Come are the best ending themes
The Meryl Johnny wedding was the most awkward scene ever as well as the Raiden's kid scene. (Really everything before the first set of credits in MGS4 was off.
Gray Fox and Psycho Mantis are my favourite characters but I pretty much love everyone but Rose.
MGS1 had the best codec companions.
I was sceptical of Peace Walker at first because Im not a fan of Mission format games but I ended up loving it