For gaming, what you're calling speed is actually bandwidth.
Bandwidth is how much data you can xfer per second. If you can play your game without it locking/lagging then this is not the problem.
Speed is how fast the system responds to a particular data request. You might have heard of people doing a google "ping" to see how fast their connection is. Good values are relative and depend on both the network you're connected to and how far you are from the target server (hence multiple servers around the world). sub 100ms is good but lower is even better.
Lastly, you need to evaluate contention ratios. Contention ratios are simply how many times the same bandwidth is sold. Seeing as not everyone uses their full bandwidth at the same time, companies can sell it a few times over. This is hardest to evaluate but to get an idea of what the contention ratios are on your network, look at 10 google ping results and see if there's a big difference between the highest and lowest values. That should tell you if there are too many people connected to the same servers.
cb