I will probably repeat a bunch of ?'s already asked. Some of these features may have been in XII or other KOF's, but I am just gonna state them for the hell of it.
Offline Stuff:
1. Hate to say this, but Capcom and Arc System Works have very strong features implemented into their training modes. Such features only help players simulate situations, further understand their opponents' options at a given time, and develop a richer understanding of the game. These features include: Record/Play option for at least 10 seconds, random option for blocking and counterhits (allows players to test hit-confirms), quick restart, walk dummy out of corner, and other features.
2. Offline (and possibly Online) Multiplayer features promoting ease on extended play. Examples being: Quick Rematch button, a way to change team order after a match without needing to return to CSS, and controller mapping in the CSS (somewhat novelty).
Online Stuff:
1. Netcode is obviously important. It determines whether one may choose to play the game avidly, or not because he feels he cannot get competition in acceptable playing conditions online.
2. Replays and the ability to watch matches of others is somewhat novelty, but enhances the overall online experience.
3. Full-featured online Leaderboard. Actually, I am quite touchy on this one. I do not wish to see hackers and cheaters polluting the top names of the online leaderboard. Maybe even multiple leaderboards for things such as: All-Time rankings, Seasonal Rankings, Win-Percentage, Friends Rankings, and Individual Characters.
4. An accurate Ping number rather than the traditional 1-4 bar color system. Allows players to more accurately understand how much latency there is between one player and another.
5. Unlockable medals and other bs. I personally do not care for this, but some feel a sense of accomplishment from unlocking visual rewards for their achievements online. These rewards cannot simply be character portraits and stuff one does not notice online. They want titles and emblems which they can brandish and brag about online. I guess it makes one feel better for playing continuously.
6. Browsing available matches. With the ability to see the number of players in a room, and the estimated Ping of the room. This feature has become almost mandatory in fighting games.
Some of the features I mentioned will not only enhance the experience of both the long-time devoted KOF players, but also newer players looking to play XIII for either leisure or competitive ambition.