With the Tess Gerritssen even if you didn't enjoy it The Surgeon is the first one in the series but they do get much better as the series goes on, try and stick with them if you can
As Karsa has said the Jo Nesbo's are brilliant starting with The Redbreast, again take his recommendations with Lee Child they are all very similar but those are defintely the best and can be read as stand alone. For John Connolly I would go back to the beggining of the series with Charlie Parker again, although not strictly speaking Police detective series Charlie Parker is a PI the mysteries tend to be a lot darker with supernatural aspects but don't let that put you off they are still in essence murder mysteries, the first one in this series is Every Dead Thing.
I will try and think of some more and scour my bookshelves I have read so many thrillers, do you like straighforward crime ones or with a bit of romance or not bothered?
happy reading