Well, I'm anal for one. Once you've seen the differences in framerates, its extremely easy to tell about or near exactly what the fps is.
For most people that don't care too much, 45 fps and up looks silky. 30-45 is a notable difference. Anything below 30 is very easy to tell.
When something is running at 20 or below fps, it is generally visually unappealing, no matter how graphically intricate it may be. Also, below 30 makes playing games rather difficult, because this is around the threshold where controls become unresponsive and lag behind from when you input.
The 3D games are definitely unresponsive with controls, which is a GOOD indication that its more than likely struggling to maintain 30 fps. It could also be just bad controls, to which I'll give then some benefit of the doubt. However, I'm leaning towards poorly optimized games, because things like pocket legends or the OG Nova, are instantly responsive, and playback quite smooth. Now, I'm no software guru here, but it makes sense to me that lagging and un responsive touch screen controls are DIRECTLY related to performance problems.
Again, the 3D aspect is relatively new for android in general here, so I'm fine with dealing through the problems that pop up. Though, the EVO 3D might be underpowered like the 4G, the new LG 3D phone going to AT&T has about 60fps playback on games, from what I could tell through the videos and not having a hands on look. We'll have to see how this all plays out.
For now though, the new games run like smashed *donkey* hole.
For the record, I can get framerate estimates from looking at things within about a 3-4 frame range. I consider that fairly accurate for human error. Still looks bad, however few frames I'm off by, exactly.