The Alliance gained six assembly places, while the three remaining seats went to a County Tyrone doctor standing on a single issue over hospital services, maverick unionist Robert McCartney and Progressive Unionist David Ervine.
Nigel Dodds of the DUP said the party "now speaks for the unionist community and now speaks for more people in the province than any other party".
But Mr Trimble said the Democratic Unionists had "sold the people a false bill of goods".
He added: "The DUP can't deliver and that will become clear and it will become clear very quickly."
The election count took two full days
Sinn Fein President Gerry Adams said it had been a good election for his party.
"There is a crisis within unionism that will need some patience for the rest of us to show in the time ahead," he said.
Reflecting on his party's showing, SDLP leader Mark Durkan said it had to "work with the hand that democracy deals us".
Following the results, the British and Irish Governments said they would "seek a political way forward and to secure a basis on which the assembly can be restored and a functioning executive quickly established".
They also promised to bring forward proposals in the new year for a review of the Good Friday Agreement.
The White House admitted it had some concerns over the outcome of the election.