Depending on the game type, you can usually drop packets and keep going because subsequent packets will make up for the missing packet. A fast-paced game such as a first-person shooter for example does not want to rely on TCP to get the packet order correct. The game should just ignore the out-of-order or dropped packets and continue on. A chess game however does not need minimum latency and can quite easily deal with the extra few milliseconds taken for TCP's guaranteed delivery.

I have found that not many games are using IPX these days. IPX was quite popular a couple of years ago for LAN games, but this popularity seems to be waning in favour of TCP/IP. DirectPlay and other alternatives such as HawkNL can povide guaranteed delivery using UDP, but they also can not get around the delays that guaranteed delivery may cause.