As you know, one's appreciation for a certain character can depend greatly on the caliber of his/her voice. Well, Gourry's character has been protrayed by two brilliant voice actors for both the dubbed and japanese versions of Slayers: Matsumoto Yasunori and Eric Stuart. Here's a bit of information about Gourry's voice actors:
Matsumoto Yasunori is Gourry's japanese voice actor, or seiyuu. Much to my disapointment, I was only able to find very little information about him:
My opinion: Matsumoto did a very memorable job protraying Gourry. But, a tiny complaint that I have is that his voice didn't sound quite young enough. ^^; Other than that, he's great!
Eric Stuart is Gourry's english voice actor, for the Software-Sculptors Slayers dub. Fortunately, I was able to find a HUGE, official website dedicated to Eric Stuart (EricStuart.com) that contained a lot of information:
My opinion: Eric Stuart performed the role of Gourry Gabriev very well! Originally, I had a bit of a problem with him, because I had a natural tendency to rebuke dubbed versions. But I got over that eventually, and came to realize what a talented and versatile voice actor he is.