Quick and easy render and good end result - Keyshot.
More flexible with lots of exta toys to play with but longer to set up -Showcase.
Max 2012 has a new lighting engine (good for interior and large scale models).
All depends on what you want it to render and how you want the end result to look.
Used all 3 and like Keyshot the best - because it's fast.
Maya is not a renderer, but it ships with mental ray by default which is quite a nice option. You can also hook up third party renderengines like vray/arnold/maxwell/turtle/octane/furryball.
I've only used mental ray a few years back and am now using vray.
Luxology Modo also has a great native render engine and it's great software to work with. Features realtime preview rendering as a separate option to your final image render.
I believe the right combination of good modeling, detailed texturing and excellent lighting makes your render great. Not so much the engine you use. Oh and add some final touches in post production. Rendering should not be your last step.