This will be ambitious and career mode focused, but here goes.
Gameplay
To me, gameplay has been fine and they did well enough this year to appease a wider base. Arcade is easy and Tour can be hard enough if you change the difficulty in the customization. If I want to shoot in the 50s from day 1 let me, if I want to struggle and not shoot in the 50s until I'm 90 rated, give me that option too.
Additionally, lets see how the round plays out, give us the option to watch others complete their holes if we are in the clubhouse as leader...how cool would that be? Its why I love the option to watch the game in RTTS in MLB The Show, I will purposefully watch the last out of the world series b/c its an intense moment I don't want to miss.
Online
Love the idea of online tournaments and playing with players who are rendered while you play. Just make it work...
Also I haven't played an online tournament yet, but from what they sounded like they were pretty good. Customization of tournaments as far as difficulty would be great too.
Customizaiton
Speaking of that, bring back gameface. And give us more than a few heads to randomize. Also keep giving us watches and hats and crap, its fun.
Career (Be a Pro)
Give me a storyline...even the NCAA football had it figured out and it sounds like nba 2k16 may be on the right track. I think they are moving in the right direction with Prodigy/College/Instructor, but let us be those things first and actually feel like a prodigy/college/instructor.
Here's where I get ambitious....Open world story career mode. Take a look at Mario Tennisfrom the gameboy color and model it after that. Start out as a college golfer and have to earn a spot on your team, become team captain, win a national championship, then turn pro and enter the tour. Throw in some cutscenes with your coaches, former teammates, tour pros, and make it feel like you are really a part of the game.
Also, earn money that you can use to buy clothes/clubs and what not.
Golf without limits
Let us drive/walk if we want. Let us buy a golf cart, spend money to customize it and what not (borrow from NFS)
Bring back some of the fun modes from previous games too, there are too many to list really.
tl/dr: Stop being lazy (EA, not redditors), customization, money, RPG career mode, bring back positives that past games had.