I overstayed my student visa in Canada for almost 2 years..that was almost 8 years ago I voluntarily left after my overstay and after moving back I have a full time job etc. here now..I want to get a visitor visa this year to visit friends in Canada, will I face any problems/rejections/bans when I apply..I have no intention on staying back and I want to just visit for 2 weeks any way I can make that clear to them? or Should I not even bother applying?
This is going to depend almost entirely on whether Canada knows you have overstayed. If they don't, you should be OK; if they do, you're very likely to get rejected.
In your shoes, I would just try my luck, and have a plan B in case you don't get the visa. Note that you will likely have to lie on the application, both about overstaying in Canada (you don't want to say "Yes" to this) and about previous visits, although this could go both ways: it's risky to say you visited Canada before, and it's also risky to omit the visit. My gut feel is that it's better to list your previous visit and give the dates your visa was granted for, but YMMV.
In any case, apply for the US & European visas first and book your flights to Paris from the US, not Canada. This was, any Canadian rejection doesn't affect them. You might also want to consider getting a new passport first, so the fact that you didn't leave Canada for two years is not obvious.