My husband made home-made tomato sauce two years ago that we still have on the shelf. It's stored in air tight mason jars and smells fine. Can we still eat this?
I would be very wary of that sauce, despite its good smell. For full disclosure, I am extremely conservative when it comes to food safety and shelf life, but here is some information that I found compelling:
WRT to average time any commercial tomato sauce can last on the shelf, a quick answer can be inferred by using this site: http://www.eatbydate.com/vegetables/fresh-vegetables/spaghetti-sauce-shelf-life-expiration-date/
It states that commercial sauce has a shelf life of about 1 year past the "eat-by" date. Your sauce, of course, has no such date, but assuming an eat-by date of about 1 year past bottling is probably pushing it. So, even a commercial product is probably on the edge of your 2 year scenario.
From a home-preparation POV, if you used the boiling-water method to preserve the sauce, I would say no, don't eat it. The pH associated with most spaghetti sauces (~5.0) is rarely low enough for the boiling-water method to be workable. Pressure-canning is an option (and if your sauce had meat or any meat products in it pressure canning is the ONLY option). If you pressure-canned, then I still think you're on the edge, but it's less scary to me.
Here's a link to a good article on that subject.