Konami's X-Men arcade game and The Simpsons Arcade Game were both recently removed from the PlayStation Network, but both games are still available on Xbox Live Arcade, a member of the NeoGAF Forums noted today.
X-Men, an arcade game Konami originally launched in 1992, was released on both PSN and XBLA in 2010. The Simpsons Arcade Game — a beat-'em-up Konami launched in 1991, was released on XBLA and PSN in early 2012.
Searches for both titles on XBLA show that they are still available for purchase at $4.99 each. Neither game shows up in searches on the Sony Entertainment Network Store.
We have reached out to Konami to find out why the games have been removed from PSN.