some of my suggestions:
- adding a dropshot skill - this came to my mind when playing my very first tournament - i had bad shots like forehand or backhand, but always could do a dropshot without problems, even if my opponent hit a smah i could have returned it with a dropshot. So like they're "service", "smash", "backhand" skills, there should be a dropshot skill.
- also if player keeps losing, his form should decline and he could gain some "form" points back as soon as he wins a match. The more matches he wins, the better form. If a player is so bad then he can't win a match, it's time for him to rebuild his career in challengers and futures
- smashes shouldn't be returnable so easily
- computer should be better when hitting dropshot at the net, he makes error in more than 50 % of cases now. Also the comp never does stopvolleys which are pretty effective way to end a rally. (I mean, when I'm at the net and hit a drop shot return while my opponent stands behind the baseline)
- more player types the two that can be chosen now, also more (and possibly optional) types of service
- more umpires (as I already mentioned), a women's voice could be nice
- some players could be moaning when hitting a power shot (like Nadal does), but this is a extra feature that I will surely live without
- the players should be "live", now they're more like robots - they could i.e. pump a fist when breaking, throw their hands up when they win a match, throw a racquet (sometimes) when they hit a silly error etc. That could be a lot funnier than now
- also the audience should be live! clapping when a player faces a breakpoint, doing that "ooooooooooh" sound when he misses an easy shot etc.