Canada is decidedly not a 2 party system. There are 5 parties in parliment in total, although the Greens only have 3 seats. Yes, 2 parties tend to hold power, but we also end up with the ruling party only having a minority (as is currently the case) from time to time which makes for a very different dynamic. The biggest difference between Canada and the US is that Canadian voters can and will act to kick a government out of office when they aren't acting in the interests of the people, sometimes shifting the makeup of the government significantly after a general election. Ridings also aren't gerrymandered insanely, so there are many seats which can shift parties.

I upvoted this because I agree that the UK and Australia have more than two important parties, but I believe that the Australian voting system is MUCH better than the US and UK systems (which also supports your main point in a way).

It's better, but it's still rubbish. The FPTP system virtually guarantees a two party system, which means that whatever one party thinks is a good idea, the other is effectively forced into taking the opposing view, and the lake of anti-competition laws (or enforcement of?) around media effectively means that Murdoch media and the Liberal/National coalition are basically wings of the same party.

Having seen MMP play out on the other side of the Tasman, it's pretty clear that MMP produces saner outcomes.

My personal opinion is that is MMP forces coalitions more often. The upshot of which is that everyone is forced to be more willing to communicate and compromise and take on saner positions, because the opposition one term may turn out to be the maker of the governing party the next.