Mr. Sinister vs. Dr. Doom... ?
First scenario: Sinister decides he needs to gain control of Latveria in order to have a large population to draw from for his experiments. He realises the severity of taking on Dr. Doom, and gives himself 3 years to prepare. During this, Doom learns that someone is planning to attack him. He doesn't know who, just that the attack will take place within a year. So now Doom has just about 12 months to prepare his defence. There are no restrictions on what Sinister and Doom can prepare, only that it's something that the character is likely to do.
Second scenario: Straight up, spur of the moment fight.
Who wins.. ?