As gamers some groups tend to fall in love with one game and that is the game they play. There are groups out there that have been playing AD&D 2nd edition for near 30 years now. They don't want to play other games, and that's perfectly fine. In other groups, they tend to play the same game but the GM - or another player - has aspirations of trying other systems out. Today I want to talk about how even if your group wants to stay with the same game, those other systems can still be of use.
Ideas Are Rarely Exclusive
The core thought behind those books being useful comes from the fact that ideas are rarely exclusive to one setting. Everything simplifies down, and plot lines and stories - the ones that seem to really resonate with people - tend to be universal.
Depending how much the genre switches, you can generally steal adventures from any game for the one you are going for. The fun part about this is as different games focus on different tropes this can bring a different feel to your game. This does take some work on your part, but it's also easier than most people think.
Consider a Super Hero adventure where Superman is turned into a villain, making a character that can't be beaten in direct combat and that needs to be saved from the mind control. This can work in a number of ways in other genres. In a game like D&D, he could be a Paladin and Hero for a Kingdom. In falling under the sway of the evil wizard there is now a powerful champion on the other side, so how do the PCs go about saving him? In Science Fiction it could be another hero, or it could be a powerful AI defense mechanism that is a halmark for keeping an area safe.
Other adventures that are less character specific can be even easier. Heists can happen anywhere, you just need to adjust the dressing to match your game. The same with wars, intrigue, and scandal based adventures.
Sometimes a game will have mechanics that just doesn't exist in other games, and those mechanics can have a lot of flavor that would work really well for an NPC you have going. Getting ideas from other games can be the difference between a good encounter and a great, or at least good and unique, one.
Yes, you'll have to make sure the mechanic works in the language the game you're running uses, but that isn't too hard to do. Having this new mechanic can really help with the development of a scene too. It brings more things into play and gives you something to build around. Best part, it's something your players likely won't see coming because nothing in the system you're using will prepare them for it.
Some games have awesome characters. Steal them. Steal them with great vigor.. You'll have to transition mechanics (getting a theme here?) Still, if you like the characters, take them. Sprinkle them into your game. Build stories around them. Play up what makes them work in the other game that's not part of the one you're in.