My ranking of the 2-D SNK/ Eolith/ Playmore fighting games, assuming you can stomach 16-bit graphics:
1. KoF XIII - the most beautiful looking of the KoF series (XIV looks like shit even if I've become used to it). At pro levels the game is broken but it's more than fine at casual levels
2. Garou - Mark of the Wolves - beautifully animated, back to basics 1v1 fighting game, SNK basically remaking SF2.
3. The Last Blade 2 - Almost as beautifully animated as Garou with a cool setting and characters
4. The Last Blade - Just as good as the sequel
5. KoF '98 Ultimate Match - the original classic that's still played in arcades in Asia. The first of the three KoF "dream fight" games, i.e. every four games SNK released a special game with all the fighters from the previous three games - this is basically the SF2: World Champion Edition of KoF
6. KoF 2002 Unlimited Match - the second "dream fight" title, and the one that's most well known in the US although this current version has seriously nerfed Athena, May Lee and Angel, which is NOT the true 2002 experience. So use a ROM emulator if you want the original arcade version. While 2002 is not as "classic" as '98, it has several new fan-favorite characters that '98 was missing including Kula and Vanessa. And as previously mentioned, the most insane version of Athena ever. Unfortunately the arcade version is the ONLY KoF without King, WTF.
7. KoF XIV - The latest title, probably a better mechanically designed fighter game than XIII, and has a ton of new characters but you have to get used to the garish 3-D character models
8. Samurai Showdown IV - For me this was the peak of the Samurai Showdown games but you could make an argument for III. Samurai Showdown is probably the most "fun" SNK fighting game series with absurd character designs and weapons
9. KoF XI - I've never played XI so I can't really compare it to XIII but it's basically the prototype of XIII and the last KoF game using the original sprites. Note that the original version doesn't have Andy, Mai, Joe, Leona, Robert, and Chang (wtf!), so the PS2 version is preferred since at least it restores Mai and Robert. PS2 version also has Hotaru from Garou which is awesome.
10. KoF 2001 - This one is significantly different from 2002 in that it uses a completely unique "striker" system, giving you 4 characters that you can either play as or serve as power-ups in other words you can choose to use 1, 2, 3 or 4 characters, and it has several interesting characters that didn't make it into 2002 including waifus Foxy and Li Xiangfei. 2001 is also the first game where Kula appears as an "official" character (she was a secret character in 2000); KoF would never be the same.
11. Samurai Showdown III - Like IV but less inspired and with less cool characters
12. Fatal Fury Special - The definitive Fatal Fury game, with the characteristic FF two-plane fighting mechanic and 1v1 (as opposed to KoF)
13. KoF '96 - The first "fully matured" KoF since it has the full Iori team (Iori, Mature and Vice), first game with Leona, AND Kasumi Todoh, who was missing from the original arcade '98. KoF without Iori and Leona is like SF without Chun Li. It also feels different than '97 or '98 since Chizuru isn't playable, which is pretty nice
14. KoF '97 - has an extremely epic feel since it's the conclusion of the original storyline, but on the other hand doesn't have many advantages over '98; '97 however is one of the most satisfying games in the series to beat in single player (more satisfying than '96 or '98)
15. KoF 2003 - The last of the KoF games that runs on MAME emulation, it has better graphics than 2002 and is the first iteration of the new storyline characters Ash, Duo Lon and Shen Woo. But um, balance issues, even worse than arcade 2002- Duo Lon is seriously broken in this one.
16. KoF '94 - '94 is an interesting playthrough since you cannot edit the teams. IE If you play with the Japan team, you MUST use Kyo, Benimaru and Daimon, which is an interesting experience
17. Samurai Showdown 2 - an early classic and it has some iconic characters that have never returned like Earthquake
18. KoF '95 - This is a more polished version of '94 that also allows you to select your own team members, but ironically that makes it less interesting than '94. Note that characters were completely rebalanced, King is AMAZING in '95.