Most of this answer is inline with my thoughts on the subject. Ruling something like "being related to video games" as off-topic on a large scale seems to be looking in the wrong direction. Games are basically a kind of software and much like the line between genres in games has gotten fuzzy over the years, so too has what is and is not a game. There's a lot out there that is marketed as a game but can be used otherwise, and vice versa.
It also gets messy when you start to look at the line between games and game development. This is something that our two existing sites, Arqade and Game Dev, have oft wrestled about. Things like map editors, mod making, and the like, where do these fit? Ultimately we shipped off the ones that deal with content creation largely over to Game Development, only keeping the stuff that's constructed inside the "play" portion of the game on Arqade. But even that gets fuzzy when you look at, say, the RPG Maker series of console games. Messy, messy, messy.
To me, though, the issues largely fix themselves just by looking at the scope and nature of what we're building here. What we're constructing is a haven for people that have something they need to get done, to find software that does that for them. We aim for those who can scope their needs to a nice set of features, but at the top level, the point is to enable someone to complete a particular task or job.
We focus on that, we knock off a good portion of game-related recommendation questions - boredom and personal desire aren't problems that we solve here. Someone who asks for an alternative to what software they're using, it's because their current software isn't doing the trick for them and they need a solution that does this trick. I ask for a new game featuring platforming witch combat because I finished Tobari and the Night of the Curious Moon, the current game is done yeah but the problem is the resultant boredom I have in not having a new game to play, and that I have a particular fondness for witches. That's not a thing we strive to solve. So by looking at it this way, we knock off the mass generic "What games fit this genre?" or "What games play like this other game?" questions that make up a large portion of the potential "threat" of feasibility of the subject matter. While we serve, on a certain scale, as a directory of options for people, we strive beyond that with our focus on solving the underlying problem. That's why we require the amount of effort in answers and the like. "Something new to play with" sits quite easily underneath all our existing rules.
Once we get past that class, though, the rest of the questions should be handled neatly by our normal guidelines and requirements. Taking a look over your example questions, 2/5 are boredom solvers / taste finders that don't fit our mission, while the other three are all too broad in varying levels. If you want to find particular mod tools, you'd approach it the same way you'd try to find a particular kind of, say, architecture software that has all the specific key features you need out of it. If you want a game that simulates certain kinds of physics or mechanics, then you ask about those requirements and you get yourself what is basically like every other software recommendation we permit, just that it happens to also be a game.
Which is really where this ultimately sits - the fact that it is a game is usually tangential. Games can be valid answers to software questions if the game happens to actually solve what the person needs. They might even be the best solution. Meanwhile, questions about games that we wouldn't like on here, quite frankly we wouldn't take whether or not they were games. That the majority of questions about games will most likely fall in this category of unacceptable is a consequence of their general intent and the general nature of the search for entertainment, but that's how it goes. That's all consequences of what someone is seeking to do - and at the end of the day, it's not our job to entertain people. We solve problems on this site - that's what the experts here are geared to do.