Obligatory, the first game in the series isn't stellar, but 2 onwards have some of the most satisfying 2D combat I've ever found. Granted I haven't played these games in a decade and am due to try the collection out that released for a replay. But I do know that when I think fondly back on these games from my childhood what I remember is not only how tough the boss of boss fights were, but how satisfying it was to play them well. I think Hollow Knight is probably the closest modern game to emulating the feel of the Zero series bosses. Each stage gives you a score based on speed, damage taken, and enemies destroyed, with unlockable skills based on better scores. There are countless collectibles hidden throughout stages in the form of cyber elves that give some fun exploration to the game. Many games in the series encourage diversifying your play style based on a sword or gun only run, but also offer customizable options in the form of equip able armor upgrades. Additionally there are unlockable NG and hard modes that let you master the game on advanced difficulty. If you haven't given these games a try they are worth it. One last thing about the combat is that it is tough but extremely fair. Some 2D games are frustrating when it feels like bosses moves are so erratic that you can't really get into the dance floor flow combat. These games definitely get it right though and reward mastery of the game.