What you are doing is called Faulty Analogy. It's a logical fallacy. The previous poster did not suggest Wil Wheaton play Kirk. Frankly, I think he probably could. He's a decent actor, and Kirk isn't exactly the hardest character to play. But no one suggested he play Kirk. The difference is that Wheaton was already known for one important character. It might be jarring to see him move from that role to another one that's even more iconic. However that in itself isn't necessarily a problem. Two words: Jeffrey Combs.