Since Jose Mourinho took charge at Old Trafford in 2016, United have spent around £286m ($404.4m) on recruiting new players. His City counterpart Pep Guardiola has splashed around £447m on signings, most of it on improving his side's defence.
City have dominated the Premier League this term, which has seen them sit comfortably on top of the table. Despite that, they have further strengthened the squad by completing the signing of Aymeric Laporte from Athletic Bilbao.
United are behind them in the second place and have strengthened their attack by adding Alexis Sanchez to their squad. The Chilean international arrived at Old Trafford from Arsenal and as part of the deal, the Red Devils allowed Henrikh Mkhitaryan to move in the opposite direction.
Liverpool also signed Virgil van Dijk from Southampton for £75m in January. The Dutchman became the world's most expensive defender and despite the centre-back's addition, Aldridge believes his former club and other top four rivals will struggle to compete with the two Manchester clubs.
"The trouble for Liverpool and the rest of the league must be that the money being paid both in transfer fees and wages by the Manchester clubs," Aldridge said, as quoted by the Irish Independent.
"Even though Liverpool got the man they wanted in this month's transfer window in Virgil van Dijk, there is now a real danger that the title race will dominated by the Manchester clubs for years to come.
"Van Dijk was a big signing for Liverpool this month, but that one eye-catching deal is not enough to keep up with big spending Manchester City and their neighbours United.
"Not for the first time during Jurgen Klopp's reign at Anfield, Liverpool look set to be in profit from player trading at the end of a transfer window and that is not what the fans want to see in this era of crazy spending.
"You look around the Premier League at Arsenal, Tottenham and Chelsea and they are not spending too much money, so the path is clear for City and United to dominate the English game for the next decade unless one of their rivals tries to stop them.
"Arsenal have tended to work to a tight budget under Arsene Wenger's guidance in recent years, Tottenham are trying to fund their new stadium and don't pay big wages to attract the top player and Roman Abramovich is clearly not going to put too much money into Chelsea's transfer kitty any more.
"With all that in mind, Liverpool may be in the best place to stand up to the financial firepower from Manchester and now we wait to see if they will do that."