The question very clearly indicated that it was about main figures of each show (e.g. Picard/Kirk/etc...) meeting, NOT about any random series crossovers of any characters.
People complained that it's an unending list, yet the whole discussion failed to provide more than 3 valid examples -all contained in a single answer.
Everything else discussing 'endless list' examples was out of scope thanks to @Iszi in comments incorrectly telling everyone that Scotty/Riker were in scope, when the original question clearly spelled out they were not via a list of who is).
It was previously discussed that limited scope single-franchise list questions are bot "not constructive" nor "off topic".
Ditto with "questions about ongoing franchise" - merely because there may be a new ST series 5 years from now, doesn't make the question invalid.