Marinakis passed the English Football League's (EFL) owners' and directors' test after days of speculation due to the allegations of match-fixing he is facing in his homeland of Greece, which he has always denied.
However, Fawaz Al Hasawi's tenure at Forest has been a steady decline in his five years with the club.
The long expected sale of Nottingham Forest has been completed with NF Football Investments (NFFI), headed by Olympiacos owner Evangelos Marinakis, taking 100% control.
On the game itself he said football wasn't easy but with hard work, a clear vision and a strong management team, a good coach and a committed squad, Nottingham Forest will now move in the right direction with the support of its fans.
Expectations are often high at the City Ground, as Forest try to discover their former glory, which saw them establish themselves as one of England's most successful clubs.
Sport director Frank McParland has agreed a contract extension and club chairman Nicholas Randall will lead two initiatives this summer to bolster community participation and youth development at Nottingham Forest.
The new era has also started with Marinakis stressing how important the club's supporters are.
A previous takeover by a United States consortium fell through in January.
There were suggestions Moores attempted to massively force the £50million price down at the eleventh hour but the re-emergence of Marinakis is now suspected to have also been a factor. He is waiting to find out whether a remaining case against him will proceed, but says: "I have nothing to be afraid of and to worry about as I have done nothing wrong".
'I had glories from my times with Olympiakos who have won everything, who have broken every record both within our country and in Europe, in the Champions League for our level.
"What we have achieved in national and European football with Olympiacos FC, we want to duplicate with Nottingham Forest".
'We know a lot of players, managers, clubs, officials in various parts of the world in worldwide football, agents - all this can help us to put all our connections together and try to do our very best for Nottingham'.
Nottingham Forest have announced Olympiakos owner Evangelos Marinakis has completed his takeover of the club.