It is undeniable that to some men, size really does matter and the bigger the better. The inventor of soft porn, Russ Meyer was evidently obsessed with highly well endowed women such as Helen 'kitten' Natividad and Pandora Peaks. Meyer's trashy 60s movies like UltraVixens made an art form of the over sized booby, and these were all natural; no surgical enhancement here.
Similarly, Howard Hughes also harboured a large breast fetish. He was so obsessed with Jane Russell's breasts he custom designed bras for her. In the 1930s, the torpedo look was in vogue, and Hughes bra was designed to enhance this effect without showing a trace of nipple. It didn't really work and Russell attained the same effect by putting tissue paper inside a standard bra.
These guys are however, the exception rather than the norm. Hughes in particular had a bizarre relationship with his mother and his breast fetish is very likely an expression of this. In my experience, size really doesn't matter to most guys.
Put a pair of boobs in front of a guy and he is biologically incapable of ignoring them, no matter what size, no matter how many he's seen before.