Lampard is a shock target for United manager Sir Alex Ferguson.
"The biggest thing for me is that there is clearly a lot of football left in Frank," Mcllroy told the Manchester Evening News.
"He's still a box-to-box midfielder at 34 years of age and that hasn't diminished. His goal figures from that position are extraordinary.
"I think it is unbelievable that Chelsea want to let him go. He's still got a good two years left in him at least. He seems to look after himself like Ryan Giggs and Paul Scholes have done at United and look how they are still doing.
"Chelsea are going to find it very difficult to replace that kind of a player but if that's the way they want it then United could get themselves a great asset.
"You'd get a return from Lampard in terms of goals and you cannot beat the experience he would bring. I would certainly go for him.
"Frank could replicate what van Persie has done. It is unbelievable what Robin has produced and Lampard is capable of having the same impact. That to me would be a dream come true.
"I think the key to all this, however, is what plans Paul Scholes has got at the end of the season. If Scholesy is thinking about retiring again then I think that might swing the decision for Sir Alex. I think whatever Paul decides might just make up the manager's mind."