I dunno, never thought about what's best 2P or 1P...always felt '95 is the absolute best, best backgrounds, best music, best roster, it's the flagship of the series until '98 came about.
...so fuck the 2P/1P ranking 'cause it's mega dumb, as for ranking in general...it's hard, all the KOFs have something that's missing on the other be it roster or abilities, each KOFs brings something unique to the table which is what I like the most about the whole series, to see the progress, the innovations, the ideas.
Top Tier KOFs
95 The best, the most classy, the real deal.
98 The second best, the real cream, total blast to play, heated!
00 The goodbye letter, the 3rd 'cause it's so zany and shiny, Charging Robah FTW!
Second Tier KOFs
96 Oh man, so good, Geese...what else needs to be said?
97 Orochi family...so good, the start of the stock system, awesome!
03 Tremendous redemption from SNK on this one, you can see they tried hard to measure up to previous efforts.
Third Tier KOFs
01 Great moveset, huge roster, largest ever I think, crazy combos, way over the top ratio system, love it!
02 Beefie Shermie...yes plz sit right on my face.
94 You gotta give it up for the classy look, so much detail, the effort is all there and it plays smooth to this day.
99 Great new system, plays great, the backdash hopforward action is way cool, Charging Robah strikes again!
If I were to rank the rest it would prolly go something like this.
4th Tier KOFs
XI
Neowave
XIII
XII
XIV
MI 2
MI 1