That's an interesting question. Let's see...
- King's Quest: KQ1-5 are full of dead ends, and the game regularly tries to trick you into getting into those dead ends. KQ6 has a few, but you're sort of warned in advance, so you should know that you need to use different save slots at those points (also you might reach situations preventing you from getting the best ending). KQ7 and MOE are dead-end free. The AGDI remake of KQ1 offers the option to play without dead-ends, and their reinvention of KQ2 doesn't have dead-ends.
- Quest for Glory: Dead-ends in 1 and 2 for sure. Maybe not in 3. There's at least one I can think of in 4, possibly more. Possibly none in 5.
- Space Quest: For SQ1 to SQ4, see my comments re: KQ1-5, except it's even worse. There might very well be no dead-ends in SQ5, but I'm not completely certain. Probably none in 6.
- Leisure Suit Larry: I can think of a few dead-ends in LSL1-5. I think LSL6 and 7 are without dead ends (pretty certain for 7).
- Gabriel Knight: I think there's only one dead end in GK1, and you get ample warning; if you actually walk into that one, you're just dumb. No dead-ends in GK2 and 3, though in GK3 you can definitely reach a situation where you won't be able to get the optimal resolution to certain sub-plots (the main story is not affected).
- Laura Bow: Probably no dead-ends in 1, but you might reach a situation from which you'll be unable to get the good ending. LB2 is full of dead-ends (and plain awful).
- Conquests series: Camelot is full of dead-ends. I'm not sure there actually are dead-ends in Longbow; at the very least situations preventing you from getting anything other than a bad ending.
Torin's Passage doesn't have dead-ends. Freddy Pharkas probably does (at least there's a timed sequence at one point; you might end up saving with too little time left to solve it).
I'm sure I've forgotten some games, and I'm sure there's a site somewhere that has all this information laid out far more accurately, but that's what I can offer.
