Modern warfare keeps updating then restart telling me that update successful hit start to...

Have you tried a power cycle? hold the power button 10+ seconds until console shutdown itself, restart the console and retry to play the game.

As additional information, after a big update, sometimes the games requiere a little hotfix of few mb, I play Warframe by 5 years and every update works in that way, big GB of update, restart the game, few KB of Hotfix and than game is ready.

If the power cycle option doesn't work, Cancel the update in your queue.

Failing that, un-install the game and re-install it

Make sure the console is up to date as well

Have you tried going to My Games and Apps and then selection Modern Warfare and hitting start on it and check for available updates? It should be sitting in there and you can easily queue it up for download.

As for the store being down, it could have been an issue on Microsoft's end or you could simply hard restart your Xbox and see if that helps.

[quote user="PlatinumSpectre"]

Modern Warfare 3 will be more successful, Battlefield 3 will be the better game though.

[/quote]

Hit it on the nail