What Player Abilities Should the Game Encourage?

[Hautamaki]

A few thoughts on optimization:

A perfect game system would allow for total customizability of your character, but with perfect balance. In other words, players should be able to build exactly the character they imagine, but they shouldn't be able to build a character that is better in every way and in every situation than another player's character. All "realistic" character concepts, within reason, should be equally viable; so I think that a game system that results in 1 player finding a way to make a character that is obviously stronger than everyone else at the same level even though everyone made an honest effort to create a viable character concept is a broken system.

 

[AbdulAlhazred]

I'm not really fond of optimization as a goal in an RPG. I'd rather see things that happen in-game be center stage myself. Options are good, and that will doubtless imply some degree of ability to fiddle with the system, but I think 4e aimed at options as player empowerment and flexibility more than as a system mastery sub-game. It might not have hit that mark, but it seems like the same sensibility would be good in 5e.

Planning and tactics are fun. These are the things I personally like, along with players really exploring the details of the game world, which can involve lorekeeping sorts of activity but doesn't have to focus on that too much. Players who build nice backstories and tie their PCs into the setting are fun. I'm not sure how much that is a system issue though. It just happens in my games.

 

[Mengu]

Note that I am answering for my preferences, even though some of the answers are about options. I play with widely varying playstyles at different times.

Optimization
I'd prefer this not have any effect at all. However, realistically any complex, rich system will have at least a bit of this. I prefer it kept as minimal as possible, but not more minimal than that in the zeal to clear it root and branch.

Preparation
I like a fair amount of this provided that it can be somewhat telegraphed and reasonably accounted for by the players. That is, I like the need to prepare, but I don't care for severe "gotcha" bits.

Knowing Your DM
As with optimization, a certain amount of effect is inevitable simply by the nature of roleplaying. The system itself should not require it or encourage it.

Knowing Your Fellow Players
Some knowledge of fellow players should be rewarding beyond the simple joys of play often inherent in such knowledge. This is one of those things where well-meaning strangers should be able to make do (especially with decent communication) but knowing everyone makes the whole thing a bit more smooth. Certainly, do not want to penalize the resulting improvements in play!

Puzzle-Solving
Puzzle-solving should be always optional--meaning readily available and easy to integrate if you want it, and easy to avoid entirely likewise. Thus the system itself should be neutral on it.

Strategic Gaming
A heavy dose of this inherent in the system is fine by me. If it's not there, I won't have much trouble adding it myself, though.

Lorekeeping
Same answer as previous, with the additional caveat that running a good mystery is as much about pacing, the nature of incomplete clues, and other elements, as the lorekeeping itself. I don't care for the lorekeeping to become central to the mystery. A little note taking and memory can be made to go a long way.

Aggressive Roleplay
Game should be neutral on this. This not only varies by campaign playstyle preferences, but can change by the hour. In an all day session of 40+ year-old players, I want aggressive roleplay at 10:00 A.M. By 6:00 P.M. I'm happy to get any roleplay at all.

Since I can't seem to xp you, I'll have to quote and say ditto on every single item on the list.