Ganbare Goemon 4 is a rather visually stunning game compared to the rest of the series, but it suffers from rather questionable design changes. The game is a primarily 2D platformer like Ganbare Goemon 2 was, but this game is a lot more brutal and precise in its platforming. Which isn't necessarily my thing, but I know some people like that sort of stuff. They have also replaced the Giant Robot Battles with Impact with mere minigames now, which is a tad disappointing. When it comes to the language barrier, this game has the most of it of the SNES goemon games, having me have to look up a guide continually to figure out what is what. And as much as you could theoretically "feel" your way through most things, one of the aforementioned Impact minigames is, for some reason, a quiz game. of which, I read very minuscule amounts of japanese, and knew nothing about what I was doing, but managed to make it through with pure luck.
If you're not a hardcore fan of the series, just give this one a miss.