a good number of well balanced and charismatic characters. smooth and fun gameplay.

A good fighting game makes a novice player feel powerful and an expert player feels unbeatable. No way should a player just be able to button mash and beat a real player. Plus, it needs balance. No overpowered characters. Every character should have moves that are unique but every character should have a move that can counter. Only exception should be the (often unplayable) bosses.

Visual flair is a must, too.

Le Smash Bros.

Which one? Each smash is pretty unique.

I think there are 2 key stages to a good fighting game.

1) easy to jump in and play with friends, so has to be initially very fun

2) a deep complexity, so that those who want to go beyond the "fun" can

Melee and brawl of course.

It varies person to person honestly.

To me a fighting game needs to have a sort of balance that the player can know to exploit abilities using quick thinking strategy. I really hate cheap difficulty in fighting games that devolve into spamming a move. There also should be tiers that beginners can enjoy simple moves, but can tell more experienced players that learn habits, patterns and develop strategies.

Independently of genre is style and aesthetics. Fighting games to me need memorable characters that add personality. As fine tuned a game may be, if it was just wire frames fighting I think I'd get bored still.

A good fighter has a decent barrier of entry for newbs but has a scalable level of difficulty for longtime fans. Open juggles help so they can be creative with their combos. For newbs Capcom perfected rush combos so if you have a gauge, you can pull off combos they would never normally be able to naturally string together. Its really about balance, the personality of your characters and the interaction with the levels. The reversals need to be fluid. It also depends on whether its 2D or 3D so you might need to be specific because they play differently.

Sexy Women?

Why not sexy men too?

Everyone's happy!