Dead thread but still an unaddressed issue
Google searched 'view notification history iphone' and saw this thread from 2011. The issue still ticks me off today when I have found that there still isn't a solution to what must be a common complain.
I feel like unless you check your notification center routinely you're still going to miss stuff that makes it useful. If I'm asleep, its likely that I will have more than 10 recent items. I wish you could make items as viewed and then refresh that app in the notification center to go back to others that you haven't marked as viewed.
You can't catch it all and that's a place an awesome feature like Notifications falls way short.