I've flown SYD-JNB (or v.v.) a few times and have overflown Antarctica (or the sea ice off the coast) only once.
For other routes that some might call "unusual," how about ANC-HNL? The difference can be quite dramatic in the northern winter. Or a couple of possibilities intra-state in Alaska, ANC-OME or ANC-OTZ. Go see the crazy seabed gold miners in Nome (or tour the remarkable, wildlife-filled Seward Peninsula) or stick a toe in the Arctic Ocean and watch the sun not set in Kotzebue, an Inupiat Eskimo community located north of the Arctic Circle. The same AS flight goes to both.