I think Tom’s right that Bush could be one of the greats, but there is much that has to be settled first.
Things are happening now in the Middle East that would have seemed impossible to any reasonable person just a few years ago. Afghanistan and Iraq are both functioning democracies! This alone is shocking, but there is so much more to the story. American actions have fueled positive changes across the area. Qadhafi, terrified by the sight of Saddam’s fall in Iraq, has been leading his country away from terrorism and back towards the international community. There has been an election in Saudi Arabia and there is going to be one in Egypt. These elections are mere tokenism will do nothing to change the power structures in those countries, but still, the fact that Middle Eastern dictators now feel the need to bow to democracy is a substantial improvement. Bush could also pay a key role in coming to some kind of resolution in Israel. He was right to hold out aganst Arafat, and he is also right to support peace in Israel now.
The recent events in Lebanon are flat out astonishing. The pro-Syrian government even threw in the towel today. This is huge, and many of brave Lebanese fighting the Syrians have said that they were inspired by the recent elections in Iraq. They have also been emboldened no doubt, by the perception that the United States is looking for an excuse to kick Syria in the crotch. The fact that the Syrians have coughed up Saddam’s brother is a strong indicator that their clothing is reeking with the stench of fear sweat. This is not only entertaining to watch, it's also good for the world.
If these trends hold, if Afghanistan and Iraq are sill democracies twenty years from now, and if they have been joined by other nations in the Middle East, historians will have no choice but to list George Bush among the greats (assuming also, that the spread of democracy leads to a reduction in international terrorism). Even if things go well I still wouldn’t place him above Reagan, who pulled us out of the economic morass of the 70’s and hastened (or perhaps even caused) the demise of the Soviet Union and its satellite communist states. Also, Reagan is the man who made conservatism respectable. It's impossible to imagine W without Reagan paving the way for him.
However, things in the Middle East have a way going into the crapper, and if this happens Bush will have to be labeled a bust. He will also have get a historical F if things go terribly wrong with Iran, Russia and North Korea. If he allows nut cases to get and keep nukes, and they later launch them on us or our allies, Bush will justly get low marks from historians (if there are any historians left among the Mad Max survivalists after the nuclear holocaust).
Also, on the domestic front, he hasn’t been that great. He throws our money around like a drunken Democrat, and has allowed the government to grow too big. He can wipe out his first term’s domestic missteps if he succeeds in passing dramatic Social Security or tax reform, but that’s a pretty big if.
Though, in the end what matters the most is how he handles the spread of democracy and the war on terrorism. These are the big issues, and if he is proven right on them he will be one of this country's greatest presidents no matter what else he does.
Tom adds: Yes, the outcome of W's foreign campaigns still do remain to be determined. I should have stated that he could become, which is what I meant, rather than he is becoming. But since I believe that all of this indeed will happen, and indeed appears to be happening, I tend to speak on this subject "as if". But even if things all go according to plan and the entire middle-east is transformed into peaceful, vibrant and prosperous democracies (and whichever other hugely positive implications this would cause on a world level) and we all get through this crucible in one piece, you still wouldn't put his legacy as more far-reaching than Reagan's? Difference of opinion, I suppose. But I did want to get you to bust out your history smarts on my ass, and you did. And yet so gingerly, I might add.