The likes of Germany have already been knocked out of the tournament while Belgium's next opponents Japan have reached the knockout stages, and the unpredictable nature of the World Cup has left Martinez impressed.
"I have been involved in the past two World Cups and knowing how it works, this is the best World Cup I have been involved in," Martinez told reporters after their game against England on Thursday.
"The games have been so, so close. The small margins will open up a little more in the knockout faces, but it has been an impressive World Cup so far."
Belgium's match against Japan in the round of 16 will take place on Monday night, with the winner facing Brazil or Mexico in the quarter-finals.