"sharp" is a fuzzy concept.
It's possible for smaller formats to appear more sharp at the same final print magnification either because of more visible grain, which can be perceived as enhancing sharpness, or because of accutance effects.
Although larger film typically contains more information (i.e. resolution) I personally do not find that the larger formats appear sharper all the time. Larger formats are often praised for their "smoothness" and "detail" but that doesn't always translate into a superficial perception of "sharpness". You may well get a sharper-looking photograph from using rodinal than using D23, even if the former developer recovers less image information.
A given film emulsion, exposure and developer will have certain MTF properties. Changing the magnification of the film image while holding the final print magnification constant is sort of like changing the "Radius" control of a digital unsharp mask.