Solas was never in love

(Dragon Age Inquisition & Trespasser DLC spoilers)

To be evil means not knowing that you are evil; you simply do what you want as long as the consequences are to your benefit. An evil person would lie, cheat, and manipulate others for his/her goal or entertainment.
Solas is not only evil, but also cursed. His curse originates from his undoings to his fellow elves. The only reason Dragon Age Inquisition has only one romantic partner with a sad ending is because, his, is the only real one.

Let me explain, Solas romances the inquisitor until they get the orb. However, the orb is broken and he cannot get power from it. Thus, he leaves his supposed love, the inquisitor, in search for that power. He leaves her right after she becomes of no use to him. As lovely and innocent he might appear to be to her, he is still evil and would still lie to get his way.
But, that is not all. As evil as he might be, he is also cursed. His soul is cursed with all the elven blood he let be shed. His curse forbids him from ever going beyond getting the power he craves. So he wanders between the Dragon Age multi-universe, trying to find a way out of a never ending cycle with each new player. He knows his curse is tied to the elves and that is why he only reaches out to a fellow elf and never to another race.

That, is the story of Solas, the evil manipulator that is cursed with the need for power he can never attain.