Alright. Let's look at the facts here.
We first see Jareth in owl form, watching Sarah, as if protectively, in the park.
Later, while Sarah is telling Toby a story, she says "But what no one knew was that the King of the Goblins was in love with the girl, and had given her certain powers."
Sarah DOES have the power to call on the goblins.
Sarah seems to have an aweful lot of things in her room that seem to have come from the labyrinth.
-The fashion doll that looks like Jareth.
-The book end that looks like Hoggle.
-The music box that plays "As The World Falls Down" AND has a dancer that looks exactly like Sarah does in the ball.
-A stuffed version of Sir Didymus.
-A copy of "Where the Wild Things Are", the cover of which shows a picture of a monster that looks very much like Ludo.
-A labyrinth game.
Jareth takes Toby when Sarah asks.
Jareth alters time for Sarah.
Jareth never does anything to actually hurt Sarah.
In the Escher Room, Jareth says "Fear me, love me, do as I say and I will be your slave." Now, how much does that sound like the "love, honor, and obey" of wedding vows?
Naturally, a few of these things can be argued against. First, Sarah having the ability to call on the goblins. Perhaps it's not just her? Can anybody call on the goblins? Most likely. Otherwise, there'd be no need for a story with the words to call on them. Unless, of course, Sarah is the only person to have a copy of Labyrinth?
Second, the things in Sarah's room. Jareth states "Everything I've done, I've done for you." Perhaps he created the labyrinth to look like what Sarah would expect it to due to her room? Or, more likely, like the copy of Labyrinth, Sarah is the only person who has most of these things, and they're all gifts, like the book, from a certain Goblin King?
And, of course, actually taking Toby doesn't nescesarily show Jareth's feelings for Sarah. It's his JOB to take unwanted children.
Verdict? Jareth is genuinely in love with Sarah. Now if only she'd just figure that out.