I've noticed that for me, somehow, I'm perfectly tolerant with just 15 FPS. 30 FPS is when it feels smooth enough, and 60 FPS is great, but not easily attainable if game is remotely recent (unless it's a DS game) *blames too much time on 5th gen consoles and anemic hardware*

One thing I've noticed is that the "acceptable" frame rate seems to vary depending on the game. On turn-based RPGs, I find 15 FPS to be good enough, coming from the time spent on FFIV DS and all the PS FFs. Action games... well, you'd need to look at at least 30 FPS + lag free, but if it's an RPG, it's sorta safe to be at the 20 FPS range, as I've noticed with Skyrim.

About the only time I game anymore is online, so I want at least 60 FPS. Anything lower isn't worth it.

Around 25 FPS for me. My laptop sucks at playing games (at least well) so I have low standards.

30-60 FPS. Usually this standard since I like seeing things moving along with the game, and not so much following with it. I'm lucky I have a computer to play these games smoothly.

It really depends on the type of game. Games with minimal graphics (RPGs) could run low enough that they only change when you make an attack or the text scrolls. First person shooters can't run any lower than 30 fps for me. Most games are fine with at least 15 fps.

If a fast-paced FPS hits below 50 FPS I start feeling pretty sluggish, and if a game is dropping frames frequently I can notice it too, but as long as it isn't going between 60 and 30/40 every few seconds I don't mind too much. Other slow paced games I tend to play on other systems so they're usually tailored for whatever specs said system has so I don't worry about FPS too much there.

I've noticed that sometimes I like a low frame rate - somewhere around 15 or less and when it's not any sort of action game. It does give the feeling of "the system is pushing its hardest to present your game", especially when it came to RPGs for 5th-gen consoles, like the PlayStation. Or how my GF2 struggled to run later games... So many memories... of bad framerates. Great memories of bad framerates.