Having played quite a lot all these "dream" cross-overs, I personally really love the first CvsS made by Capcom, with a decent effort in terms of visuals (pretty great versions of the SNK characters), some main Capcom characters redrawn (Ryu/Ken/Akuma/Vega) but already, some copy pasted ones from Alpha that really didn't mesh quite well with the others in terms of art-style. Especially the girls who were quite tiny in terms of scale, and Morrigan was horrible with her black pixel underline.
CvsS2 was an absolute horse-shit, looked like shit, characters that weren't homogeneous in art-style, character selection screen with portraits that were poorly outlined etc... This game was so bad, it is the culmination of Capcom losing all their skills in 2D production, Marvel vs Capcom 2 and Capcom vs SNK 1 being the first games to be a testimony of this.
On SNK side, they had competent artists. SVC Chaos has always been a fan-favorite of mine. The pixel art is gorgeous, there is a post-apo atmosphere that actually drove the overall art-style, rather than being a bland mash-up of everything. Character choices were nice and varied, Capcom rendition were magnificent. Gameplay is fast and lacks impact, they actually made choices to have a single play-style, rather than copy-pasting all playstyles from all games like Capcom did.
The NGP fighting game is a blast and one of my favorite fighting games. It is absolutely timeless, has awesome characters, 3 fighting systems that just work, additional bonus games to unlock attacks. It looks good and plays like a dream.
Finally the NGP Cards game is honestly a bit poor. Cards look awesome, but the strategy in this game is really poor overall. This one is clearly overrated. Once that you understand that you need to stuck your opponent with cards at 100/200 HP, you are basically going to win most of the matches on your first try, so it becomes quite repetitive.