The PS2 is an excellent consul with a large library of titles, but it is outdated. The PS3 is certainly not cost effective though, and of the "next-gen" consuls you might look at the Nintendo Wii or X-Box. The Wii is about the price that the PS2 was and can be used with a regular controller or the motion sensing gizmo. The X-Box has the largest range of titles, and as an extra bonus for schools they can even be used to teach young people how to make games with the XNA sdk and C#.
You are right in saying that the X-Box has the largest range of titles amongst the next-gen systems and that it would be ideal to teach students how to program games. If I would have had that in my youth I would probably be a game developer instead of an ESL professor. However, my main concern (since I live in a place where English is the second language only by legislation but people see it more as a foreign language) is to expose the students to language in a fun way (meaning not Mark Twain, as great of a writer as he is it I think he should be used only in universities), make them think, and make them react. If I can expose them to a story or two, then all the better. With that in mind, I think that while the Next-Gen consoles have great potential, I don't think that any of the three are quite ripe yet, either as gaming consoles or as classroom tools. I have never seen a gaming store that carries more than 15 Wii games at a time, and the only RPG that the Wii currently has is Twighlight Princess, with a Dragon Warrior title and a Final Fantasy title on the works. The 360 seems to focus more on FPS, 3rd person action-adventure games, and sports. The only RPG I have seen for this system is Phantasy Star Universe (also available for other consoles). The PS3 is backwards compatible with PS2 games, but only with 80% of the games. I don't know the full list of games, but I have heard that it is not compatible with any of the Final Fantasies (PS1 or 2) or with the Xenosaga games. That is why I have not gotten one for myself yet. Also, most of the PS3 games I have seen seem to be remakes of the Dynasty Warriors games, although the prommise of a Beowulf game and Final Fantasy 13, as well as Oblivion make it seem like the console with most RPGs. Although all three are great systems with great potential, I would be hesitant to recommend them to any school, at least for ESL purposes. I do think that the Wii with Trauma Center would be a great adition for ESP students who are going into medicine or nursing, but that's the extent of it. Before recomending one of those, I'll wait another year or tweo and see what developers have in store for us. Besides, the PS2 is not entirely outdated yet. Its graphics and sound actually surpass those of the Wii (although nothing is as fun as four grown men and their wives playing Wario Ware) its titles are more appealing than those currently in existence for the PS3 and the 360 (perhaps with a few exeptions from the 360) and I honestly doubt that there is a gamer out there who has experienced all the games that the PS2 has to offer. I have every RPG published stateside for the PS2 and I've only played about 40 of them. (about half). That's about 80 RPGs total for the PS2 (not counting the ones from PS1). None of the next gen systems have 80 games total, that's why I vote PS2.