What if S�leyman had succeeded in conquering Vienna?

Not really, the Persians were at the time just waking up to what would be 250 years of very bloody conflict over Afghanistan with the Mughals. So for once the Eastern Flank was secure. And with the fact that the Turks may have been welcomed in German places with a protestant symphaties, esp if they went against Rome. Perhaps they might notnhave been able to hold C Europe for more than a century, but the history and future of Europe would have been very different. England might have stayed out of the whole "there can be no supreme power on the continent" policy they followed from about that time till 1945, France might have abandoned its attempt to expand to its natural borders (which led to most of the wars a hundred years later). Or protestanism might have been another aberration in the history of the Church abandoned once the Turkish threat became literally "in your face".