"Parallax" --> The Enterprise encounters what looks like a doppelganger of itself. That A-Plot can be easily made to be TNG. The B-Plot of Torres vs. Carey can be dropped and replaced with something else.
"Time And Again" --> A planet has to be saved from destruction caused by the Enterprise.
"Phage" --> The Enterprise encounters the Vidians for the first time. They try to harvest some guest crewmember's organs. Picard alerts Starfleet Command about them, so Starfleet will be watching out for the Vidians in the future.
"The Cloud" --> Because of TECH the TECH (this is mid-'90s Star Trek), the Enterprise ends up in a Cloud where it encounters a being that wants to mate with the Enterprise. I didn't say this would be a great episode, just showing how it could be done.
"Eye of the Needle" --> This episode has the most purely VOY premise since "Caretaker". The only way it works is if TECH takes out the Warp Drive, the Enterprise needs to help from anyone within communication range, and it turns out to be a Romulan. The send the messages to their families storyline would have to be dropped.
"Ex Post Facto" --> Riker is accused of the murder instead of Paris. Sounds like another version of "A Matter of Perspective", but an eighth season show doing something
similar (but not exactly the same) as what it did in the third season isn't unheard of in the world of television.
"Emanations" --> Any TNG character can be in Kim's place and transported to a world where everyone thinks they've come back from the dead.
"Prime Factors" --> With modifications, this can work as a TNG episode. Just bring a third party into the mix. The Federation and the Ferengi are both interested in a technology that can catapult a vessel across tens of thousands of light-years. The hosting planet decides against sharing this technology, the Ferengi try to steal the technology, Picard has to stop them. The premise works for TNG if you put it in a different light.
"State of Flux" --> The Enterprise investigates how Federation technology ended up in the hands of a hostile race. Doesn't have to be Kazon, just an Alien of the Week.
"Heroes and Demons" ---> Just another wacky holodeck adventure. This time, put Data in the role of The Doctor. And have Worf along, since Medieval Earth would be right up his ally.
"Cathexis" --> An invisible alien threatens the Enterprise. Wouldn't have sounded out of place on late-TNG.
"Faces" --> This is another one that needs to be changed from the original premise to work, but can be done. Doctor Crusher is kidnaped by the Vidians in hopes that she can cure them of their condition. The premise of someone like Torres being split into a Human half and a Klingon half would have to be dropped.
"Jetrel" --> A scientist on one world who was responsible for a terrible weapon being used on another, a member of that race still feeling bloody-minded about it even though the scientist regrets the way in which his weapon was used. Switch it up to where Picard has to mediate peace between these two worlds and you have the perfect TNG story.
"Learning Curve" --> Riker, Geordi, and Troi are temporarily sent to another ship with a crew that's not up-to-snuff, and they have to bring them up to a point where they can be up to Starfleet Standards. Meanwhile Picard, Worf, Data, and Crusher have a B-Plot Adventure on the Enterprise that eventually ties into the A-plot where they couldn't have solved whatever was going on without the help of the crew Riker whipped into shape.
I can also include the four VOY S1 episodes that were held over for S2 and the DS9 S3 episodes written by TNG S7 alumni, but I'll leave it here for now.