Feel free to justify if you wish.

Batting average is still arguably as important as on-base percentage to me. OBP does not say that you are advancing baserunners, gaining more than one base yourself, or driving in runners. The statement that "a walk is as good as a hit" is not true, except in rare cases. A walk is almost as good as a hit.

Gotta go with RBI's over the rest.
Good examples would be Harmon Killebrew. He drove in 1584 runs with only a .260 batting average.
Also Ernie Banks with 1636 RBI's with a .274 BA.
Give me a player that drives in runs over a .300 hitter any time.

Batting Average.
OBP.
OPS.

Offensive Rankins

1. OBP I mean come on, if you're on base it still kind of counts as a hit!

2. AVG.

3. R.B.I.'S

4. HR's

5. Runs

Batting
RBI
OBP
Slugging

Nope. The stats have been calculated. Batting average is meaningless. A walk is not as good as a hit, but the difference between making an out vs not making an out is much much more important. It you want a simple test and you know a little stats, you can run a simple correlation in Excel on the various stats versus team runs-scored. You'll see: OPB matters, BA does not.

The top two stats are OBP and OPS (OBP+SP). If you really want to know who's contributing the most, there are various Runs-created formula, or just take 1.8 x OBP plus SP.

You can find Runs-created (RC) and RC per 27-outs on ESPN.com

I have to laugh at people who say batting average is more important than on base percentage. I want players on base, period. You have to have base runners before you can advance base runners. i would rank the top stats like this


rbi's
runs
homeruns
obp
avg

I like homeruns as much as the next guy but all that really matters for your team is getting runs in or scoring them.

Baccheus is correct, Avg. is meaningless. For those of you hung up on RBI, that's a non-important individual stat also. It tells you more about a team then a player. Players ahead of "player x" get on base, then "player x" gets credit for driving them home. You could have the most incredible player in your lineup batting fourth; but if no one ahead of him is getting on base much, he'll have a low RBI count. OBP is, far and away, the most important stat in baseball. The most important thing for an offense is to get runners on base. The more runners get on base, the more runners will score. The order I would put them in is:
OBP
OPS
SLG
RUNS/AVG/RBI/Home Runs are all pretty equal in un-importance for an individual compared to the big 3.

1a. OBP
1b. SLG
3. plate appearances or games played (depending on what I'm looking to learn)
4. hits
5. walks
6. homers
7. doubles
8. runs scored
...
15. batting average
...
632. RBI
633. game-winning RBI

1. ops 2. slg 3. obp