One player tag, two players, enemy attack who ever is closer?

You could have a little algorithm that deter$$anonymous$$es it based on a few different factors; like player's health levels, or the aggregate of health and armor. You could invert that functionality based on difficulty level, so that the enemies go after the stronger of the two on easier levels.

Just some thoughts...

I was thinking more along the lines of whoever is closer. The better player shouldnt be punished for being better lol. I gues what I'm asking is how to deter$$anonymous$$e which game object is closer to the enemey object.

If you already know the position of the two players and the enemy you can do something like:

 dist1 = Vector3.Distance(player1.transform.position, enemy.transform.position);
 dist2 = Vector3.Distance(player2.transform.position, enemy.transform.position);
 if (dist1 < dist)...

If you are asking how an enemy finds the players, there are different ways depending on the structure of the game. Start with Physics.SphereCastAll().

I'd like to stick with what I have already, since it almost works. I'm sure I'm just overlooking something. Unless the 2nd method you mentioned has noticeably better performance.

Oh, well your question to me seemed phrased like you hadn't made up your $$anonymous$$d about who the enemy was going to attack and wanted input.

Since that is not the case, robertbu's answer is correct.

If you concerned with performant code, and didn't want to use Vector3.Distance(), then you could also do:

 float
     d1 = (transform.position - gameObject1.transform.position).sqr$$anonymous$$agnitude,
     d2 = (transform.position - gameObject2.transform.position).sqr$$anonymous$$agnitude;

 if (d1 < d2)...

http://docs.unity3d.com/Documentation/ScriptReference/Vector3-sqr$$anonymous$$agnitude.html