UPS is usually good with getting people their pre-orders, I've never had a problem with my pre-order arriving on the date they say it will. Now, time is a completely different story. I've had amazon say 5pm, and it'll get here at 10am. Or visa-versa. I think it all depends on the UPS branch and what deliveries they have for the day. I think they mean more like a "by 8pm" than a at 8pm.
UPS has been on time for me more often than FedEx. Besides, depending on which warehouse they are shipping your copy of the game from, it may not have to travel far. Still, you can't guarantee that it will arrive on time no matter the carrier.