Robin Antonick, creator of the first version of Madden, is now suing Electronic Arts for millions of dollars in royalties and a portion of the profits. He is demanding a jury trail in California, saying that his programming and call-playing expertise in the original title has been reused by EA.
As for why he is only suing now, he claims that he was not "aware that Electronic Arts did not independently develop subsequent versions of its Madden NFL software" until the recent 20th anniversary of Madden. In the complaint, "according to recent statements by Electronic Arts founder Trip Hawkins, the current generation of software apparently derived from software developed by Antonick".
In cases like these, companies like EA tend to hand out a large settlement instead of going through possibly years of litigation, but doing so might set a dangerous precedent where anyone who claims that their work was in any way used in future titles would have grounds for a substantial payout.