The  only thing holding me back is the lack of offline play.
Thats it for me. Theres allot of great games on there but the fact that you won't be able to play them if you decide to move your xbox to a room without internet.
 
For some people it's lack of achievements, and quality But theres actually some great games on there

How do i add a pole?

When you are making a topic on the right side of the screen it says "Would you like to make this a poll" or something

Them being available here for starters.

Achievements.

As long as it is a good game, I will usually try the demo and if I like it I will purchase it. 

That hundreds are out there and so many look like crap --- I'm not sure anything could get me to buy one.

I'm done with indie platformers. Make it another type of game and I will check it out.

A stunning recommendation from a source I trust. It's not something I require of most games, but I would want one before I start spending time in the indie catalog.

I'm not some Hipster out in search of a new scene.

Achievements!? they should be allowed 10 or up to 20 gs just for the fun. the highest being 5g and the rest 1gs.

How do i add a pole?

Shoot 1Up or whatever its called on Xbox live. I love that game, WISH I could play it offline.
 
*Edit
 
Its a shoot-em-up spaceship game but instead of controlling one ship you control a fleet and you keep adding to it. It's awesome. 
http://www.mommysbestgames.com/shoot1up.html

If it looks good, I'll buy it. A lot of Indie games are more original and interesting than any of the ones the big companies are making.

Applejack.  Throwing fridges at pandas making them burst into thousands of coins.  It's good.  The fact they have no achievements is also a great thing.

Probably some really good word of mouth.

if somebody says  something good about the game. it looks like a good game from watching videos.

Technically the fact that they aren't available here in The Netherlands (oddly we can make them, just not buy and play them). I do buy some on my US account however and actually it doesn't take much. If the game is fun (I like the Cthulu saves the world game a lot for example) and they are cheap I easily buy them. The addition of achievements would be great. But I guess Microsoft is scared that without moderation people will start abusing it to up their gamerscore.