So I'm going to break down the information of the series and films and determined by an educated guess which girl Tenchi really loves. 'Course, what do I know? This is purely opinion by observation!

Tenchi Muyo!: Now, Tenchi is pretty indecisive here. When Tenchi first thinks Ryoko died when she attacked him he said, "It's too bad she died, she was kind of cute." Tenchi also shows feelings for Ryoko when Kagato takes her. Tenchi also likes Zero when he thinks she's Ryoko and after they merge. Tenchi also feels things for Ayeka during Muyo! when he sees her graceful princess attitude, but the crush dies soon because of Ayeka's other ways...Tenchi first shows his affection for Ayeka in third episode, Hello, Ryo-Ohki!, where she twists her ankle and Tenchi takes her back. It started to rain so they both took refuge in a lil shack thing. They go on a walk or two and that's about it. There wasn't too much romance in this series. Hmph!
Who won: Tie--Ayeka/Ryoko!

Tenchi Universe: In the beginning Tenchi had a lil crush on Ryoko which soon dies, but with her clothes and her behavior; what guy wouldn't? Ayeka comes; another crush that quickly dies. There was that lil sweet potato thing with Ayeka, she takes it from him; too hot, lil scream, drop the potato, Tenchi rushes to check her hands. Ummm, well there's not much else until we to the time and space adventures. There's nothing in the first two that's worth mentioning but in the third one it's Ryoko's world. Tenchi smiles warmly at Ryoko a couple times and when Ryoko comes back to denounce the world she takes Tenchi's hand. Now, she didn't grab it, it was very loose...until Tenchi squeezes back! Tenchi tries to tell Ryoko something which could have been I love you or something (Ryoko tells him to stop or they might never get back). Later Ryoko's looking at the sky on the top of a gate...thingy...and Tenchi throws her an apple, takes a bite, grins goofily and winks at her; Ryoko smiles warmly and takes a bite of the apple (awww). The only other time Tenchi shows any feelings for Ayeka is when he goes to get her back from Kagato. Back to Ryoko! Well Tenchi shows obvious feelings in the last couple episodes when Ryoko is hurt and just look at No Need for Ryoko! Tenchi says that he'd love to go on a journey with her! In the last episode when Tenchi's walking he's thinking about "the carnival" when he think he sees Ryoko behind...but she fades out and he also thinks he sees Ryo-Ohki, but it's his cat, Chibi. Then Ryoko REALLY appears on a rock, says "hey." and jumps to give Tenchi a hug! :) He hugs her back, she whispers some sweet words in his ear, they look at Ryo-Ohki, and then they walk off hand in hand! AWWWWWWWWWW!!!
Who Won: It's CLEARLY Ryoko

Tenchi In Tokyo: Now, there is no doubt Tenchi loved Sakuya. But I don't usually count her because A) She dies/disappears at the end of the series, B) Tenchi gets over her, C) Her only purpose was to make Tenchi love her and seperate the bond between them and D) It's my theory that Tenchi ONLY loved her because she was a normal girl (I mean we all know she's not prettier than Ayeka or Ryoko)or that Sakuya may have had some power that gave her an edge! o.O' I also don't like Sakuya...until the last time Tenchi sees her, that was sad! Anyhoo, forgetting about Sakuya...In Ryoko's Big Date! Tenchi holds Ryoko's hand and even says HE'S ATTRACTED TO HER!!! ^!^ Also, in the last episode Tenchi and Ryoko almost kiss...but then WASHU BUSTS IN with her dimensional portal! hmph, too bad.
Who Won: Duh, Sakuya, but then Ryoko! ;)

Movies: Ok, who always ends up saving Tenchi's sorry butt in the movies? RYOKO! Tenchi Forever, Ayeka even said Ryoko was the only who could bring Tenchi back!!! lala ^_^ Daughter of Darkness; Ryoko goes with Tenchi! Know what else? Ryoko is the ONLY girl who appears on the side of the boxes with Tenchi (only Tenchi Muyo! In Love and Tenchi Forever have this). Mhmmm, kinda leads to think good things about Ryoko, eh?
Who Won: DUH Ryoko!

Who won overall: Ryoko!