Its interesting that none of the successive actors after Weller even closely resembled Weller, not even with mouth which is an area that the actor works with with the character. Peter Weller was chosen for a lot of reasons, but one of them was also because, according to Paul Verhoeven, he had an interesting face, he was very Mannequin-like which fit the character. Weller had an almost feminine, short but thick lips and an elongated face, which placed his lips higher up.
Every actor after Weller had completely different, wide and thin lips forming a bitter arch shape, and were closer to the chin as oppose to Weller's which were closer to the helmet line. That's one of the reasons why other actors just never looked right in the gear, they looked alike among themselves, but completely different from Peter. Therefore, they looked like someone dressed as Robocop rather than the Robocop.