There may be more Subway locations than McDonalds', but I'll bet MickeyD's shows substantially more gross revenue. Just because you can open a Schlubway in every strip mall from here to Kingdom Come doesn't mean they make any money.
Actually Subway is following exactly McD's expansion pattern, in both franchises and revenue, but having read the McD's book they managed to shave about 15 years off the clock. McD's crossed 10,000 stores in the mid-80s, SubWay crossed 10,000 stores in only 10 years. And of course for most of the 10 years McD's has been suffering through some very bad decisions that have seriously hurt their bottom line, they tried to move away from their core market of burgers and lost tons of revenue because of it; they finally listened to every business analyst on the planet a couple of years ago and went back to being a burger joint and the profits have gone up, but they lost a lot of expansion opportunities in that era.
But that's the reason why Subway is making money. They don't have to spend money on brick-and-mortar stores.