Are Pixar and Dreamworks too similar?

A BUGS LIFE (Nov 1998) / ANTZ (Oct 1998)
Similarities:Small ant trying to make a big difference for his colony, falls in love with the princess ant, battle to save the day. I think these two films have the most in common compared to these other examples.
Differences: Z's romantic interest with Princess Bala plays a bigger part in the movie compares to Flik and Atta in Bugs life. Flik and co charcters have a more cuddly appeal (child-friendly and marketable).

FINDING NEMO( May 2003)/ A SHARKS TALE (Oct 2004)
Similarities:Little fish in the big see, battling scary sharks who are in fact friendly.
Differences: Marvin(nemo) raises awareness in the community to find his son.Oscar(sharks tale)raises awareness to advance his own reputation.

RATATOUILLE (Jun 2007)/ FLUSHED AWAY(Nov 2006)
Similarities:Rats who lose their home on land and end up in the sewers
Differences: Remy has a passion for gourmet french food. No love interest.

MONSTERS INC (Nov 2001)/ SHREK (May 2001)
Similarities: Scary monsters who are soft on the inside, save the girl, both have entertaining sidekicks.
Differences: Shrek is in the style of a fairytale with multiple exhisting characters. The monsters are doing their daily job in a different realm.