Zangief

This match up is pretty much a polar opposite to Sim; you almost never want to be close to Gief. If he manages to close distance, your safest option is to backdash (flipping is NOT safe). If Gief corners you, you're in trouble. With his arsenal of 50/50 setups, Gief can really hurt you if you're cornered. There's no way to jump out, since his lariat will always catch you. Your options are to backdash (which suffers the risk of being baited and punished), to RH or EX Scarlet Terror (which suffer the same risk), or (which I think is the safest option) cr. jab xx ex walldive to the other side. It's safest to backdash after you take a second to block because most players will follow through with their block strings once started. So, you avoid whichever normal or throw or special that Gief decides to end his block string with. The only downside to this is that SPDs will almost always catch you if you decide to block on wakeup. So it's a huge 50/50 game in the corner, but if you play a runaway Vega, you're almost never caught in this type of situation.

The key to keeping Gief away is to abuse your walldives and pokes. Although, you shouldn't really attempt an Izuna Drop or Barcelona Attack because the lariat will ALWAYS stuff your attempts if it's input properly. Walldives are strictly for building meter and escaping if you're being pushed towards the corner. Gief doesn't really have a safe way to close distance on Vega. If you're sitting with a charge, there's little Gief can do. Reasons being:

-Blocked green hands can be punished by several things (throws, cr. strong xx EX walldive, cr. short into rh Scarlet Terror)
-Giefs jumps risk being AA'd by Scarlet Terror.
-I forgot which normal it is, but Gief's rh? normal (the one that moves him forward) can be punished with RH or EX Scarlet Terror or cr. jab into whatever.

So, basically, this matchup is supposed to be played similarly to most of Vega's other matchups (where Vega gets the life lead and has you chase him). And with Vega's many keep-away tools, you can easily frustrate Gief players into blunders.

Also, focusing right outside his SPD range is VERY useful.

Overall Matchup: 5:5 (Gief can really hurt you, but he has to catch you first )
Best Normal: st. rh