Captain America. He's the gold standard for marvel he's undying will to fight even with the odds against him he's scene of knowing right and wrong to the point of surrendering at the end of the civil war knowing that they most their way. He inspires all heroes to rise above themselves he's lead countless of marvels greatest heroes and all says that there is no greater leader than he.
Doom is always a villain. Morbius and Venom are on the list because they are anti-heroes, while Magneto and Juggernaut have had their turn at being villains but have also been heroes for a lot of the time.
Doom is a villain ALL the time.
Doom has been a hero on a number of occasions. Most recently during Hickman's FF. Magneto's always been a anti-hero most the time anyway so I'll give you him, but Doom has probably a hero as often as Juggernaut has.