By the best lens for photojournalism, I think we need to define photojournalism a bit more. What I do, which is more documentary photography, is long-form photojournalism, and I find having a 28/2, 50/1.8, and 85/2 or 135/2.8 in my bag does just about everything I need to effectively tell a story.
If, on the other hand, we're talking hard news photojournalism, getting those great shots of today's building fire with a tight deadline, then a zoom is really the only way to go.
Still, too much of a case can be made for the long, huge white lenses. We're not shooting for National Geographic, after all (OK, maybe some of you are). I've shot a number of events with nothing but two primes and an OM4t, while other media photographers shot the same event with their giant lenses. By the time the photos are resized for online publication and posted to a site, there is little or no difference between mine and theirs. You'd be surprised how many photos on major media web pages were captured with iPhones and Blackberrys. Alex Majoli covered the Iraq war and other news events with nothing but a P&S. Editors just aren't that picky anymore.