Mark Scheinberg remains the Isle of Man's richest person, according to the Sunday Times Rich List.
The 45-year-old co-founded PokerStars with his father in 2001, building up the world's biggest online poker company, before cashing out in 2014 for £3.3bn.
Despite his £3.5bn fortune, Scheinberg saw his wealth fall for a second year.
He is one of five individuals on the island who boast fortunes in excess of £1bn.
Robert Watts, who compiled the list, said: "There aren't too many islands with five billion-plus fortunes. But the Isle of Man - with its well-documented tax advantages - still draws young and older members of this gilded class to its shores."
"Just three of the entries on our Isle of Man Rich List have seen their wealth rise over the past year - and four are worse off. This casts doubt on the belief that the rich only ever get richer."
Canadian online gaming group Amaya, now known as the Stars Group, bought Pokerstars and Full Tilt Poker in 2014.
According to the island's Gambling Supervision Commission, there are 36 e-gaming companies currently licensed on the Isle of Man.
Winners and losers
Nine people - or families with a Manx connection - feature on the list of the 1,000 wealthiest in Great Britain.
Scheinberg is followed by Alki David and the Leventis family (£2.6bn) who are second on the Isle of Man rich list after recording the largest net gain of £400m.
The Leventis family merged their Greek bottling business with Coca Cola to create Coca-Cola HBC, the largest bottler in Europe.
Property tycoon John Whittaker, 77, made the biggest loss in the region with his wealth falling by £300m to £1.95bn.
Meanwhile, "master investor" Jim Mellon and Preston-born Trevor Hemmings retain their billionaire status, according to the list.
Isle of Man's richest 2019
1. Mark Scheinberg (£3.54bn) - down £12m
2. Alki David and the Leventis family (£2.6bn) - up £400m
3. John Whittaker and family (£1.95bn) - down £300m
4. Jim Mellon (£1.1bn) - up £100m
5. Trevor Hemmings (£1.025bn) - up £25m
6. Dan Craddock (£500m) - no change
6. Mark Shuttleworth (£500m) - no change
8. Steven Lamprell (£302m) - down £17m
9. John Morphet (£55m) - down £5m
Source: The Sunday Times Rich List