Zangief's strategy centers around the spinning piledriver like the USSR's strategy centered around nukes, they inflict egregious amounts of damage and the threat of them allows for effective psyche games. His standing MK is an effective poke, his standing HK is a competant anti-air and his crouching HK is an effective trip. E. Honda's flying headbutt can be stuffed with a crouching LP, and a jumping HK properly aimed can cut the HHS off. Ryu is suprisingly easy, the spinning clothesline passes through fireballs and a single missed DP leaves him right open for a SPD. In my experience its Vega who gives the biggest resistance, you simply have no counter to his jumping HK and his pokes.