IMO, if I were to make a fighting game and I've love to. I'd incorporate these things as best as possible.
-As best balance as possible, tight gameplay that appeals to both casual as well as hardcore audiences
-Patches/updates(if possible)
-Cool, developed characters with a neat backstory, powers, fighting styles etc
-Diverse selection of characters(MK does this very well, example not just all "humans")
-Preferably 2D hitboxes and 2D gameplay
-Hot chicks for eyecandy and style
-Throw escapes/techs
-Block button(my preference)
-Good training mode like ones we've seen in MK9 and 3D MK's but that and even more deeper, various practice options from having the dummy attack with any of all of their attacks, to doing their combos to you so you can experiment with different defensive tactics, to them doing their special moves over and over to again train you to defend around it or just them sitting still. Also have more record options too like currently.
-Have around 30-40 characters max
-Have DLC, more costumes, characters and arenas
-My game would have blood, scarring, messed up clothing similar to MK
-A super meter of some sort
-Standard 1 on 1 options for 2 players
-3 to 4 players options too
-Finishing moves
-4 player option like MK9, tag team style. Both offline and online, but with an extra option to have 4 individual players or friends tag each other online to help each other, not just 2 online on one xbox, as oppose to 2 online via another xbox or one player controlling 2 characters in tag team matches(which I'd also have available.
-Have a KOTH room with however a lock option from 4, 6, 8 or 12 option or free join option with no limit based on the creators choice of course, but would also have a free open challenge option like in MK9's current lobby's.
-Option to instant recording of training, matches off or online to youtube via your account from the game within via an automatic application(one time fee of 5 dollars and you have this option forever on your console since this is saving a lot of time, work and money on cams, uploading etc) Some games have this already such as Dirt 3, but sadly isn't mainstream as it should be.
-Practice mode with online options so you can practice with a friend in just training if you wish
-Training/practice mode for finishing moves like MK9 as well as special moves, movement etc
-Storyline mode, with an MK9 style cinematic sequences while you play
-Create a character mode, very deep, layered options one per-profile. NOTE: you can take them online like MK A however, with locks and KAK and non-KAK rooms, lobbies. Ranked matches and player ranked matches, KAK not allowed. Also, something newer that's only been done in a DSi and 3DS app game called "Photo Dojo" where you make your own fighting characters based on yourself, friends etc you could make/record "sounds" for your fighters special moves, this is something to be honest I'm surprised nobody has taken advantage of yet in a fighting game with a KAK option, especially the Kinect with their mic options as a standard now. But I'd offer the option, instead of choosing from 100 different voice "tones" which I'd also have available preset, I'd give you the option to make your own, record and upload your own "grunts, screams, punches, etc, etc" into your own character.
-A combo system like MK9's where you have a few little automatic dial up strings, but the rest you as the player have to make up to your desire. Yet make it accessable to the casual player as well with having easy punches, kicks, special moves.
-A tournament mode set up(think MK4's tournament set up or MKT's) however with online and offline options, brackets etc. Tournament mode would have an exclusive room online for people who want to hold little tournaments from 8-16 players options. Everyone else watches in this mode, while the rest wait to play whoever they have to play whoever with a week save option via a vote, tally from everyone in the room so next time you log on or set up to do so, you'd be able to continue otherwise if everyone leaves, it's done. I'd also toy with the idea of having the creator of the tourney be able to save it for a few days at least depending.
-An idea that has yet to be done in a fighting game, allow to create a Clan option with members who join to be saved on the games server(example, similar to a leaderboard stat but with a clan board) with this, have an option for clan tourneys online, leagues etc(sports games have this option these days) I think this would be really cool if implemented in a fighting game.
-Instant replay mode, like DOA along side with the record options with every single match you play off and online, pausing options, frame shot, take picture options if you want to take a clip, shot of a fight and save it
-Standard arcade ladder where you beat the game, unlock alternate costume(like MK9)
- Either motion comic endings like MK9 or movies/cinematic like MK4
-Standard difficulty options from easy to max, blood or no blood(no blood having no blood or fatalities, finishers) and a handicap option like the older MK's had(where one player who is weaker has full heath, his foe you can set however you like heath bar) standard music, sound options, brightness etc
Ok lol, if I have more ideas to come I'll add or re-edit this list but I'd want all of the above in my fighting game.