The former Blaugrana striker has watched on from afar as the Spanish top-flight has enjoyed an era of domination when it comes to collective and individual prizes.
The last four Champions League crowns have been shared between Barca and Real, and six of the last nine, while Messi and Ronaldo have split 10 Ballon d’Or prizes.
Their efforts have helped to eclipse rivals from across Europe and around the world, but both are now into their 30s and Lineker admits their sudden departure from the game could leave a sizeable void for others to exploit.
He told Planet Football amid a renaissance from English teams in continental competition this season: “I think the Premier League clubs were miles behind, but we are creeping closer and we see that by having five teams in the [Champions League] knock-out stages.
“I would say we have halved the gap that was there a couple of years back, and with the money in the English game we should get even closer in the next couple of years.
“You have to remember that Real Madrid and Barcelona have a magical appeal to players all over the world and can generally sign who they want, but they have had Cristiano Ronaldo and Lionel Messi at their peak for the last few years, which has been a deciding factor in so many big games.
“The two of them are now getting towards the back end of their careers, and when they go, which sadly for all of us they will, it is going to be impossible to replace them.
“The exits of Ronaldo and Messi will level things quite significantly because those two players have been so far above everyone else in the world game for an extended period of time.”
Barcelona and Real have their sights locked on European glory once again this term, with the Blancos looking to take the title for a third successive year.
They currently hold a 3-1 advantage over Paris Saint-Germain heading into the return date of their last-16 encounter, while Barca are locked at 1-1 in their heavyweight tussle with Chelsea.