Georgia is weak, Chechnya is tough but small and Russians were brutal and thorough in dealing with it, Syrian rebels are divided and Russia has Assad regime as foot soldiers. Ukraine is a much different beast. It has close to half million troops, with obsolete but still powerful Soviet arsenals, it also has western support. I don't know why people underestimate the Ukrainians.

the ideal outcome is that the war ended with truce, and Russia has control over eastern ukraine. But I'm afraid it is not that easy. With western support, Ukraine will not tolerate the fall of its eastern territory to the Russians. They will keep sending troops to regain it. Russia will have to reattack Ukraine hinterland to stop the Ukrainians from attacking east, and the war will going on and on, until one side collapse. I'm not sure which side will collapse first. The fastest way to stop Ukrainians from attacking Donbass region is probably if the Russians use its nuke, that might scare the shit out of Ukrainians and their western supporters, but then Russia will have to face the isolation from the world. Not even China can help Russia if that happen.