My two cents:
Big loss for Russia and Iran which is good for US obviously.
Gain for Israel MAYBE given the weakening of Iran, Assad, Hezbollah; however, unclear what the new regime brings.
Gain for Lebanon: freed up from Iran, Hezbollah, Syria stranglehold. Better for Maronite Christians and Sunni Muslims in Lebanon and independence from foreign powers.
Unclear to me what this means for Turkey.
Probably a net gain for Egypt and Jordan (Sunni alliance and less Muslim Brotherhood type refugees)
but this all depends on what kind of regime emerges:
Is it more of an ISIS type regime? (bad)
Is it a decently run more reformist regime like the original population segments who opposed Assad? (good)
But VERY HAPPY Assad is gone. He has made Netanyahu look like a saint and there has been nonstop talk about Netanyahu and hardly any mention of Assad lately.
Who knows?