I play mostly very long games, too. There has never been a single short game on my list of favourites, ever. I require quite a bit of time to get invested! Kirie's the one who told me about Backlog Blitz and we sort of talked about that stuff, as well as what to do about games that have no actual ending, etc, like Mario Party or Tetris...if they go on the backlog at all or not. Counting your games as more than 1 based on length gets into a 'perceived value' area, rather than something concrete, if that makes sense. Plus everyone takes a different amount of time to finish things. Liar Princess is supposed to take 5 hours. But I was only 1/3 done and already at 6 hours. (And I'll probably never finish it, as sweet and adorable as it is. I hate platforming, lol. I was just so interested in the fairytale setting and story! But getting through each chapter is like pulling teeth, for me.)
It's not like getting a high total is 'winning' or anything since the only thing you're up against is your own backlog; the blitz is just a method of tracking how many games you buy versus how many you actually play. I've actually found the Backlog Blitz is super useful in showing you your habits and automatically curbing spending...or so it worked for me, anyway. If you end the year with a negative number, you're buying more than you're able to play and your backlog is growing. That's all it really is.
Keeping a list of the actual games played automatically shows how much time must be invested, imo, at least on a basic level. If my list is full of ten games like Xenoblade, Trails, Tales, Breath of the Wild, etc, you can see that it represents massive play time, even if you're comparing it to a list of thirty games like Liar Princess, Wandersong, Oxenfree and Kitty Love.
You could also always include your play hours on your list, if you wanted, beside each game.
Of course, you can do as you like, even if you use the blitz method. The Backlog Blitz is meant to be a method to encourage gamers to actually play and complete their games (and has the side effect of curbing purchasing, ime, and getting me to try older games to see if I can finish them after all.) So far everyone I know who's tried this counts every game as one, regardless of length, but if you found it more motivating to count it based on time, you'd need to make a consistent system to stick to.
Making my own system made things too complicated for me, so I stuck to '1' for everything, regardless of length. Except games that were literally more than one game, lol, like the Atelier Dusk Trilogy bundle. I'd count that as 3 because it is, in fact, three separate games.