To me what makes a good sight is 2 things.
1. They have to be fast. That means visable and large enough to see. Since most shootings occur in seconds, I have to be able to aim effectively with BOTH EYES OPEN. This has been contested by several ex-military guys who squint and shoot, but if you do this, you are more likely to "tunnel vision" yourself and delay shooting time. It may kill you if you have multiple opponants.
2. It has to be accurate. This one should be obvious why.
I like the 24/7 Express (XS Big Dot) or Sig sights....anything with the line/dot setup. Whenever you have 3 dots and you shoot with both eyes open. It looks like 6 freakin' dots. Way too slow...way too confusing. The line and dot will still double vision on you a little BUT, it will still be the dot on top of the line. There is no question which one is the front sight. Eventually you will notice your eye dominance. Which is important, but another discussion.