3 wins by default since i haven't played 1 or 2, but i imagine 2 holds up better than the first. so for me it would go Sengoku 3, 2, 1. the characters, the animation, music and combo-system in part 3 make it my favorite.
really need to play 2 though because i feel like i'm missing out on where the series came from.
3 by a far. 1 and 2 have this crazy ass goofy thing going on. Plus the transformations are just straight out lame. Turn into a cowboy? The graphics are very dated in the orginal 2 and just dont hold up to late neo titles. Style is so much better in 3 than the other two also. It just really is no contest.
Sengoku 3 is one of my favorite Brawlers, the first 2 don't feel like brawlers more like quick kills like sunset riders mystic warriors and shit. I like all of them but 3 is great, plus if you are a brawler man you know 3 is right up to par with Gaia Crusaders, KOV, Gladiator and all the good later era brawlers. A lot of folk don't like brawlers 'cause they credit feed through them.
On another topic but somewhat relevant, I still hold X-Men as my faorite brawler of all time followed closely by Sengoku 3 and D&D SOM, my problem with Sengoku 3 and Gaia Crusaders is that after the second or 3 rd stage all the enemies are dwarfs, but I guess it only adds difficulty to combos and juggling which is fine to hone the skills anyway.
Edit: Can't forget about Captain Commando, Battle Circuit and The Punisher. Those are awsome! I also feel like the Slammer series and AODK are kind of a fighting game with a Brawler feel to it, I love that shit!
I've only played Sengoku 2 on my DS but the combat felt really solid and I'd like to own the cart one day. As for the two I own, 1 + 3, I'm going with 3 because its fun for mindless beatmup action and the character animations are an attention grabber when guests are over.
While 1 & 2 definitely have the far better overall atmosphere and presentation I'd say 3 wins by a long shot with it's excellent gameplay. Yeah the backgrounds are mediocre at best, and the game is repetitive as all hell as well (can we get some more baddies?). However, the controls, hit detection, and combo system are fantastic.
It'll never go down as a classic beat em up, but it does manage to have those qualities which aren't just sorely lacking from Sengoku 1 & 2 but also from every other beat em up on the Neo Geo.
And for the tangental..
In my books Final Fight set the bar for how a beat em up should play and control, and I never figured out why SNK didn't bother with simply cloning Final Fight's overall gameplay with their early beat em up efforts. It's nearly inexcusable to me, after all some of these titles came out 2-3 years after Final Fight. I suppose some people might actually like that sort of gameplay in their beat em ups, but I can't imagine they would amount to any substantial number.