Game On! Librarification of games or arcadification of libraries, you be the judge.

Here's how I would go about choosing a system for a public library:

1. Review your library's mission. If your library doesn't have one, start writing. It is important to know what your library's mission is so that you can evaluate how gaming can dovetail with that mission.
2. Set your budget. It would be horrible to do all kinds of research, decide the Playstation3 is for you and then find out you can't afford it.
3. Decide what kinds of activities you envision sponsoring with your game system: family fun nights? tournaments? boys activities? girls? age groups? Are you in it for fun? Education? Both?
4. Anticipate resistance. There are going to be some people who Just. Don't. Get. It. If you've done your research and have a plan, you wll find it easier to persuade the haters.
5. Research what others have to say about the subject. First stop: ALA.--here and here. It's important to get the "company line". Then hit the blogs. You'll get tons of anecdotal information that can help you make a sound decision. Next: ask your patrons. Whether it be casual conversation, a forum, a survey on your library blog, or a more formal SurveyMonkey, you need to take into consideration what your patrons want.
6. Don't forget peripherals. The game system is not just the unit. Make sure you know what games are out there for your system and what other peripherals you might need (controllers, dance pads, joysticks) you will need to get maximum fun out of your chosen system.
7. Choose your system. My system of choice for libraries just getting into gaming who might anticipate some resistance from patrons or their board would be the Wii. It's non-threatening to video game newbies (of all ages), with simple easy-to-understand controllers but still lots of fun. There are games for a wide variety of ages, and lots of games that all ages can play together. This way, you can include the whole library community and not just kids. My stepfather loooooves bowling on the Wii. I could see starting a senior program in addition to kids/teen programs. The Wii is a versatile, non-threatening system that doesn't have a Grand Theft Auto stigma attached to it. Also, you don't want your programs to skew to one age/sex group. Gaming can easily skew to tween and teen boys if you don't have a varied program that will appeal to all. The one down side is that you cannot play the Wii online, so if you envisioned tournaments with other libraries, you would be limited.
8. Explore online gaming options or even none at all. Perhaps your library isn't ready for full-on system gaming, there are a lot of games on the net, including educational ones, and there are ways to work wth these to create a program. It's not a shame to know your strengths and weaknesses, and more than OK to decide that gaming isn't right for your community.

I think the most important part of the process is determining your library's mission and how gaming will contribute to that. To simply say "It will bring more people into the library" is not enough of a reason to start a gaming program in a library. It needs to contribute to more than just foot traffic to be justified. It needs to be an integrated part of what the library wants to do and should be doing for the community.