Pelo comentário do OP acima, este foi o filme animado de 2003 Elysium , que não deve ser confundido com o filme de 2013 do mesmo nome.
Por uma resenha em beyondhollywood.com :
... about an alien race called the Elysians who invades Earth after one of their ambassadors is killed during a diplomatic mission. A full-scale invasion of Earth is ordered by the Elysian’s supreme commander, a General name Necros. Using superior war machines, including giant skyscraper-size walking robots called mechas, the Elysians easily conquer Earth, leaving small remnants hiding in underground shelters. Soon, we learn that three of the survivors are destined to lead the human leftovers to freedom — or at least out of those dinky underground shelters.
One by one, the chosen humans are whisked away from certain death by a mysterious woman who lives in another underground base where three giant mechas also reside. The humans are told they were destined to pilot these mechas against the alien invasion ...
A resenha inclui a seguinte imagem, supostamente tirada do filme: