Lizzy was an incredible band, and I rate their Live and Dangerous a lot higher than Live after Death, although Maiden is my favourite band. Lynott was not a great bass player, but a fantastic singer. Some of their songs are real masterpieces, among which Emerald (my fav'), Mexican Blood, Massacre. I clearly remember the night Lynott's death was annonced on the radio. I was really sad, because I was hoping they would reunite one day and that I would be able to see them live.
That said, those recent tours with a new singer are just a terrible shame. I don't know how Lynott's mother has approved such a move. I mean, Lizzy was Lynott. Apparently not legaly, as Downey must have owned part of the name, but this band touring without Lynott is like Sabbath without Iommi or Maiden without Harris : pure non sense.