CenturionZ_1:
Alexander - I'm pretty sure he didn't conquer Greece but only ruled it... his father (Phillip) did the conquering there. Really all Alexander conquered was Persia and a few kingdoms in Anatolia. Still, not bad for a drunk clubman.
Archimedes - Perhaps both he was both greek *and* carthaginian - greek by genetics but carthaginian by citizenship?
Caesar - Which Caesar are we talking about here? First there was the Caesar family, which were the first few roman emperors and by the time someone kicked them out, their family name had become synonymous with the job so the new emperor adopted it as a title... so many Caesars... in fact, up until the late 19th century and early 20th century, russia's ruler was a tsar and germany's ruler a kaiser, I'll let you guess what those were derived from.
Cleopatra - Yup, Queen of Egypt, but not egyptian. She was in fact descended from Ptolemy, one of Alexander's generals, and was probably more macedonian than egyptian.
Xerxes - From what I remember, the persians lost that battle... but they still razed Athens. If the athenians hadn't evacuated in their boats and won the naval battle at Salamis (due to some problems in persian policies), they would have been dead not just homeless. From the persian point of view, the greeks were more of an annoyance (like cockroaches that just won't die) than a serious threat.