Quite a few of the XSI users(for example on german xsi-forum.de) think/thought that Autodesk actually just wanted to buy XSI to get some money from it and then stop development on XSI and just go on with a standalone ICE which then would get integrated into Maya and Max. Either they have been wrong or the sales are going so good(which on of the Softimage guys from Autodesk stated somewhere although he wasnt allowed to post exact numbers)they cant just stop development. That is/was just speculation though.
In Germany Max is on top of the (gaming)-industry, though.

Anyways, Id use Blender or the Mod Tool. Although maybe Blender has a bigger community than Mod Tool alone... If youre planning to render scenes/clips etc Id go with blender, modtool always overlays text over renders and you have a 400k or something tri-limit.

Edited my post.

Mod Tool specifically may not have a large of user base as Blender BUT Mod Tool is so close to the full version that it's more like Mod Tool users are included in with the massive user base of XSI. Even a big title I'm sure you all own TFU was done with Softimage, I honestly haven't heard of anything outside of Unreal done with Max where if I go on polycount I see tons of game models posted with XSI.