Well the reality is he shouldn't necessarily have said what he said initially. Most people knew that going into Syria would have been a cluster **** and we should be doing everything we should to stay out of it. That was the best compromise at the time, which is perhaps a positive for Obama in not pushing for full scale intervention - unlike Cameron.
If we had gone in very little would be different to now, still hundreds of thousands dead, still a fight between three/four factions, still a broken country and still terrorism rife, the only difference being there would have been thousands of US/UK soldiers dead as well, and we would have had to make the decision of spending another decade fighting in a country that has collapsed or just leaving it to it's fate like Libya, after we "liberated" it.
I still think we took the best option at the time, and I doubt things would have been that much better. Look at Libya for example, split in two, with an internationally recognised "government" that can't control a teapot, and another "government" that also lays claim to the country, all surrounded by terrorist groups now given free reign in most of the country and countries surrounding it (such as Mali - the French did a good job there, helping a sitting government deal with a rebel incursion, not dismantling a country and leaving it to go **** itself, which is what we did to Libya and to an extent Iraq).