Early RPGs, particularly the ones that expect the player to spend time doing nothing but gaining experience and levels (or the equivalent in the game).
If I am burnt out on such games, often a 2D platformer is what I need.
Sometimes I enjoy faster paced turn-based RPGs that don't require much excess leveling, such as the original SaGa.
Modern RPGs are actually not really my thing; WRPGs are too actiony, and the real-time with pause combat in the Infinity Engine game feels like the worst of both worlds (the pause and need to order each character means it doesn't work as action, yet you don't get the nice rhythm of turn based combat), while JRPGs became too cutscene and mini-game heavy starting with Final Fantasy 6 (Final Fantasy 7 being particularly bad).
Leroux: RPGs and open world games are quite good at giving you that feeling of advancement and accomplishment even if you only play for a short while
Personally, I find this not to really be the case, at least not for most games that are called RPGs.
If I want to feel like I can make progress in a short time, I look for a game like Zelda 2 (especially if it's not your first time playing), SaGa 1, or Magic of Scheherezade. Those games are quite dense in terms of content per time. Just try going back to Zelda 2 (or 1, for that matter) after playing one of the 3D Zeldas (Ocarina of Time or later).