It's all relative.
Smith - he's not great, but the Chiefs would ultimately be no good with Daniel or Geno Smith or whoever else they could've had. In the most literal sense, he's the most valuable player on the team. 1-3 without him, I'd say.
Charles - he's the best player on the offense and the only guy who can consistently be relied upon to get yards. Without him they would very likely be 1-3. I don't know that they'd beat the Giants with Knile Davis replacing what Charles did today. And they damn sure wouldn't have beat the Iggles.
Poe - he's taken a huge step but no, he's not the MVP at all. Simply no argument for him so not worth discussing.
Hali or Houston? - no. They compliment each other and if either hadn't played a snap, they'd be at least 2-2.
Sutton - I can see an argument. I don't really wanna make it. But it could be. The question is how good they would be anyway with Reid, Dorsey, new QB and plenty of FA help.
Reid? Again, you can make an argument, I think.
Albert? I don't think he's quite good enough to say MVP, but from the perspective of who replaces him (hard to say Fisher would suck at LT since it's his natural position, but...)? I dunno, man. It could be real ugly. It certainly was when he went down, albeit an unfair sample size.
Smith's the literal answer, Charles is probably the right answer. The offense is Charles, the defense isn't reliant on one guy.