Susan Richards (Nee Storm) / Invisible Woman

Main Comics (616)

 * 1)  Reed Richards / Mr. Fantastic  - Her fiance from the beginning.
 * 2)  Namor  and Susan shared a mutual attraction, despite her engagement to Reed and their being on opposite sides of law and order.

Susan and Reed were, of course, eventually married.

That didn't stop Susan from kissing Namor on at least two occasions (Namor the Sub-Mariner #50 & Fantastic Four: 1 2 3 4 #2). It was also made clear that she was still very attracted to him during the events of the Civil War

Minor Incidences

 * 1)  T'Challa / Black Panther  - After first meeting te Black Panther, while engaged to Reed, Susan and T'Challa spent some time alone together in Wakanda, at night, that seemed to hint at an attraction and even the verge of physical intimacy.
 * 2)  Peter Parker / Spider-Man  - Not even revealing his secret identity, Spider-Man asked Invisible Woman out on a date, and just to make Reed jealous, she agreed.
 * 3)  Scott Lang / Ant-Man 

Object of the affections of...
 
 * 1)  Ben Grimm / The Thing  - This was only referenced in the early issues.

Ultimate

 * 1) Reed Richards / Mr. Fantastic
 * 2) Ben Grimm / The Thing

Other Various, Individual AUs

 * 1) Ben Grimm / The Thing - In one AU, Ben was the one who married Susan rather than Reed, with Reed living in self-imposed exile afterwards.
 * 2) Namor / Sub-Mariner - These two are married in one AU.
 * 3)  Victor Von Doom / Doctor Doom 
 * 4)  Black Bolt 
 * 5)  Logan / Wolverin e - In this universe, she is Madame Hydra
 * 6)  Steve Rogers / Captain America  - This was only hinted at in Marvel Comics Suerheroes.

Fanastic Four (first cartoon)

 * 1)  Reed Richards / Mr. Fantastic 

Fantastic Four (second cartoon)

 * 1)  Reed Richards / Mr. Fantastic 

Fantastic Four Film Duology (2005-07)

 * 1)  Reed Richards /  Mr. Fantastic  - These two are shown to have been in a relationship some time ago, before becoming the Fantastic Four, but broke it off because, once she wanted to live together, Reed let himself think too  much about it instead of just acting and doing it.

It's suggested that she and her boss Victor Von Doom are in a relationship, and this is clearly what Reed believes for most of the film. Victor even proposes to Susan at one point, who does not get the chance to answer. After getting their powers, with Von Doom now becoming a threat, Susan tellls Reed "There is no me and Victor. There never was.

Reed and Susan fall back in love, and are later married.

 Fantastic Four (2015 film) 
 * 1)  Reed Richards / Mr. Fantastic  - A budding attraction between Reed and Sue is only hinted at.