I can't launch eclipse from either terminal or gmrun but I can do so using Applications -> Programming -> Eclipse.
Here are the screenshots:
1) Using Gmrun: I can see that gmrun is recognizing the eclipse command but when I enter it, nothing happens.

2) Using Terminal: when I type eclipse, I get the following message:

Thanks!
eclipsebinary to thePATHenvironment variable. This method is quite standard, quick, and elegant. – Eliah Kagan Aug 10 '12 at 22:36