bill001g :
You WANT a wireless adapter or your only option is a wireless adapter. All wireless adapters are subject to interference which causes random delay and packet loss. Most online games do not tolerate either of these well.
So if you can run a ethernet cable you should.
After that the adapter is only half your problem. It does not good to buy a adapter that has features not supported by your router. Also speed is not the critical component in game play. Most games use well under 1mbit/sec. Besides even the slowest wireless is faster than most people internet connection so unless you stream video INSIDE your house pretty much any speed adapter will be fine.
The key part nobody will really be able to tell you is how good the coverage will be in your house. If you read the reviews every adapter on the market is loved by some and hated by others. Mostly this is because all of the better adapters have the exact same radio chips and the exact same coverage and the difference are people houses.
Now I could like the previous post just link some device with no explanation but I don't since there really is no right answer. It is almost impossible to predict. But some people think the bigger numbers is always better that is how the vendors con people into buy things they don't really need.
He, and countless people like myself are looking for a suggestion that will fit the bill. you do a stellar job of not actually answering the question. you show that you have solid, nearly encyclopedic knowledge of the technology, and I'm sure a lot of people appreciate that, however most of us are looking for an answer, not an education. Saying "hey i think model x or y might suit your needs, you might check with one of the folks at best buy(or some other electronics store) and give them the specifics of your situation to make to make sure you don't get something you don't need." is goal here, not your elitist philosophic gobbledygook All you sound like when you give three paragraphs of situational variants, followed by no suggestion whats so ever other than "run a cable" which they all ready said wasn't an option, you sound not only like a self righteous douche bag, but a deliberately unhelpful self righteous douche at that. When lay people approach these sites, we want short, concise answer. Not a lesson/discourse on the ethics and marketing in the electronics industry. ill take dudes link with no explanation over your self righteous soliloquy any day. Better a wrong answer than no answer.