Let's face it; Gourry is a very sweet but blindingly naive individual, so when it comes to romance, he doesn't seem to have much experience. ^^;; But, thankfully, the brilliant creators of Slayers have managed to tastefully include several innuendoes of romance unto Gourry's path, and thus he has been paired up with practically every character! Let's analyze his relationship/chances with a few of his companions:

Note: The probability of each pairing (written in percentages) was acquired via The Love Calculator. It's a nifty little machine. ^^

Lina Inverse
Probability : 96%
Wow... 96%? This Love Calculator tool thingie sure is accurate! ^^ As you already know, Lina Inverse and Gourry Gabriev are the intended couple in the series. They have nearly the same personalities (except Gourry does not perceive/grasp things quite as well as Lina does), and they have acquired the same, laidback lifestyles. Quite frankly, these two accomodate each other's needs very well, both as traveling companions and as lovers. They're perfect for each other, in short.

Amelia Wil Tesla Saillune
Probability : 68%
68%? Hm... the probability for this couple is not very high, and I'm not surprised. Amelia and Gourry rarely interact -- why, they're hardly even friends! They're merely acquaintances. In fact, the only *real* Amelia/Gourry scene that I can remember was during TRY, when they were paired up together by Jiras. Gourry told Amelia that she was growing tall, and Amelia replied by mentioning that her older sister was almost as tall as Gourry. o.O That's such a meaningful (sarcasm) scene, no?

Sylphiel Nels Rada
Probability : 69%
Sylphiel, like Amelia, doesn't stand much of a chance with Gourry. Although I admit that this is a rather popular pairing, one should realize that Sylphiel's hero worship for Gourry means nothing to him. Gourry only remembered Sylphiel as "an excellent cook," and plus, Sylphiel lacks the leadership/dominating qualities of Lina, which are rather crucial for a lasting relationship.

Filia Ul Copt
Probability : 41%
The odds are definitely against this couple, which doesn't come as much of a surprise. For one thing, Filia thinks that Gourry is a pervert for lifting up her skirt (even though it was purely out of curiosity). She's a bit too narrow-minded to realize that Gourry is merely naive, and not perverted (don't get me wrong, I adore Filia, but you have to admit that she's kind of unnegotiable. o.o), and she probably could not accept him for his lifestyle in the way that Lina does. And, there's one more thing... they look terrible together. I know that this sounds like an odd reason, but don't they look like they could be siblings? ^^;

Zelgadis Graywords
Probability : 67%
Zelgadis and Gourry get along pretty well... but they don't really interact that often, except for the sake of comic relief. As for lifestyles, they are as different as can be -- Gourry is extremely laidback, whereas Zelgadis is uptight and bent on finding a cure. In short, they would just end up getting on each other's nerves if they became a couple. o.o