Gaming and P2P
Gamers are one of the two user types that have the most difficult time with routers. The problems stem from the conflict between the way games connect to and use the Internet and the way that NAT-based routers work. Add in the fact that there are few generally accepted standards (although Microsoft might argue with this) for how Internet based games communicate, and you may have a difficult time with online game play. And if you want to host a game server, there will be some additional hoops for you to jump through.
One thing you don't need to worrry about in gaming router selection is ping time. Any router you buy today is going to have a ping time lower than the 1 mS that ping can measure. Ping performance is always dominated by network traffic, both on your LAN and on the Internet. Quality of Service (QoS) technologies like Ubicom's Streamengine, which is used in D-Link's DGL-4100/4300 "Gaming" routers, can only prioritize traffic on your LAN.
So if you like to game and have a Bittorrent download going, QoS can help, as long as you don't try to use more bandwidth than your ISP provides. But once the packets hit the WAN side of your router, there is nothing you can do to affect the time it take for them to reach their destination.
Recommendation: The key to online gaming success is a router's flexibility in letting you open holes (ports) in its firewall. Get a product that supports as many mapped or forwarded port ranges as possible. Also look for models that support triggered mappings (this is also sometimes referred to as "Special Applications"). I also recommend you do a Google web and Google Groups search, or ask around in your favorite newsgroup or game website forum to see what works for other people.
You'll also want to choose a router that can support the large number of simultaneous connections (sessions) that are used when a game tries to find the available game servers. Unfortunately, manufacturers generally don't provide this information, so once again, you'll need to Google and ask around in gaming forums. You can also check Which Router Reigns Supreme for P2P? to see how many simultaneous connections some popular routers can handle.
Finally, make sure that your router can put one computer completely outside its firewall (called "DMZ" or "Exposed computer"). Strange as this may seem, there are some products that won't allow this, because of the security risk. But it is a helpful troubleshooting tool to see if closed ports are what is causing your online gaming problems.
That's it for the overview. Now lets move on to understanding router terminology and features.