The difference is that the Soviet Union was a monolithic expansionist power with the capability and opportunity to become a continental hegemon. Had we not intervened in Europe they would have attained it with negative results for us.
China is not yet to that point. But I fear that if we follow the neoconservative path, we will be exhausted as a nation when the time comes that we have to do serious balancing against China as we did against the USSR.
Radical Islam and the Middle East is not a monolith but a mix of often competing groups. Between Israelis, Persians and Arabs, Sunni and Shiite, the locals of the Middle East are quite capable of finding and sustaining a balance of power while requiring a whole lot less intervention from the USA.
You make some good points. I would dispute your last paragraph especially, though. How can Israel, for instance, create a workable balance with its regional enemies when those enemies are irrational and developing nukes? Imagine Iran without a US presence in Iraq and Afghansitan currently.
Also, one cannot forget that during the Cold War not only did we contain from a military/strategic standpoint, but we also contained an idealogy — or perhaps more accurately — we introduced and buttressed freedom in regions that previously had not had it, and in so doing developed long term allies.