It's all about the art, not the tool. You can make amazing environment art in any 3d package. The industry is pretty split between Maya and Max. They both have their strengths and weaknesses, but they're so minor it's not worth switching apps to overcome them. Plus, the communities are so large that you can easily find scripts or plugins to overcome any shortfalls.
There are two hurdles to making great game art: The tools hurdle, and the art hurdle. The faster you can jump the tools hurdle and get that out of the way, the faster you can work on jumping the art hurdle and making great looking work. Stick with Maya and push it as far as you can. Employers want to see amazing looking artwork and don't usually care about how many packages you know. It's relatively easy to re-train somebody on a tool, it's excruciating to re-train somebody as an artist.