Reed Richards / Mr. Fantastic

Main Comics (616)
 
 * 1)  Sue Storm / Invisible Woman  - They've had their ups and downs, but these two were engaged from the beginning, married sometime after, and have remained so ever since. She appears to be the only object of his affection.

AU

 * 1)  Johnny Storm / The Human Torch 

Fantastic Four (first cartoon)

 * 1)  Susan Storm / Invisible Woman 

Fantastic Four (second cartoon)

 * 1)  Susan Storm / Invisible Woman 

Fantastic Four film duology (2005-07)
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.
 * 1)  Susan Storm / Invisble Woman  - 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.

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

Fantastic Four (2015 film)

 * 1)  Susan Storm / Invisible Woman  - A budding attraction, mainly on his part, is only alluded to here.