"What does the first two Ozzy albums have? Crazy Train?" You're kidding, right? If you want to discuss "the most well known songs in the rock/metal genre," Crazy Train exceeds everything on either of the first two Sabbath albums by a country mile.
You are wrong. Crazy Train is not any more popular than "Paranoid" and "Iron Man".
No, I'm NOT wrong, and it's getting awfully tiresome to read your comments like this, which presuppose that your opinions are irrefutable and universal facts.
"Not any more popular" among which group of people? What evidence do you have of their comparative popularity? Of course, you could have rightly asked me the same question. Had you done that, my answer would have been more or less what Stadler wrote: Crazy Train is well-known and enjoyed by folks who are not fans in general of Ozzy Osbourne or hard rock/heavy metal. The song is ubiquitous at sporting events, and it turns up with some regularity in television commercials. Among fans of metal/hard rock, the three songs might be on relatively even footing, but Crazy Train is the only one of the three songs that transcends to the general population.
On top of that, Crazy Train, as a single, is certified 4x Platinum by the RIAA. Notably, it was certified Gold in the mid-2000s and certified 2x Platinum in 2009 and 4x Platinum in 2020. If anything, it's gaining popularity. It's also notable that Blizzard of Ozz, the album on which Crazy Train appears, is certified as 5x Platinum. A lot of that was a result of folks re-buying the album on new media, but the 5x certification occurred in early 2019. Do you suppose that's happening on the strength of I Don't Know and No Bone Movies?
Now let's look at RIAA certifications for Paranoid and Iron Man. Paranoid, the ablum, went Gold in 1971 and was certified 3x Platinum in 1986. It went 4x Platinum in 1995 (26 years ago) and that's it. How about the songs? Neither Paranoid nor Iron Man has even been certified Gold (and yes, both songs were released as singles).
So...your move. What objective evidence do you have of your assertion that "Crazy Train is not any more popular than 'Paranoid' and 'Iron Man'."