If you're playing them, your don't really stand to gain much, even if you leave the games and all inserts, etc. in immaculate condition. As stated in the last post, you should go sealed, and try to find games that only released in certain regions in limited quantities, and keep them sealed. Even then, you seem to be going after games using an SNES model. Chrono Trigger on the SNES always goes for a lot (way more sealed), so therefore CTDS will follow that, right? Not necessarily. It's all about quantity shipped and availibility. I see all the games you mentioned all over the place all the time, whereas I rarely see Electroplankton.
Still, a lot of what has raised in price these days has gained popularity through other game releases etc. Original Harvest Moon, Chrono Trigger (new IP for Square at the time and sort of a gamble), Shantae on GBC has a new title coming out, etc.
You also have to be careful with re-releases and DLC making the actual games decrease. I can cite Marvel Vs. Capcom 2 on that one.

I think what people are saying here is sound. Enjoy the games, or become a collector of sealed ones, but don't expect a profit now or later down the road when doing either.