John Gotti was known for his expensive and fancy suits, but have yo noticed how nice Michael dresses in the trilogy (especially 2 and 3) compared to the other gangsters?

I suppose you're right...however, in the earlier scenes of GFII, once he's attained 'Don' status...young Vito is dressed pretty dapper himself.

In the way he carries himself as well as the clothing...Vito's demeanor is completely transformed from an everyday goodguy immigrant to a suave, confident leader.
Much like Mr. Gotti.

Except for the apparel, Don Michael's qualities do not come across quite as happily.

Apple

I don't know about that. Altobello and the other Dons on the comission in part III were dressed nicely. Also, Joey Zasa beats him for the award of best dressed gangster. Michael Corleone doesn't strike me as any resemblance to John Gotti. He lured Hyman Roth into a false sense of security by praising him, I don't picture John Gotti doing that to his enemies. Michael didn't stand out from the others by his attire though. Other Dons had nicer clothes, especially the one who wouldn't leave his coat during the helicopter attack in Part III.

Im not saying Michael is like Gotti at all as far as personality I was more talking dress, I guess Im more referring to GFII, look what he wears in Cuba and just the stuff he wears around the compound in Tahoe..You are right Apple Young Vito does dress snazzy also, bu Older Vito's dress was a little more plain...

Michael dressed the way he did because that was his style. It also helped reveal his power within the organization. I wouldn't necessarily compare him to John Gotti as to any other gangster.

David Thomsen, the erudite British film critic, notes that ever since GFII, Pacino's Michael Corleone has "set the standard" for all filmic gangsters and gangster wannabees. He meant in dress and in behavior.

I heard that Senator Geary always admired Michael's suits and hairstyle.

...and the Corleones admired his taste in women...