Both Metroid Primes rendered the leaves in their vegation just fine, with solid framerates, in more interactive game worlds that PS2-crop RPGs tend to not dare create.
Sure PS2 can do this. Have it run at 20fps like the first Kingdom Hearts. It fits well with all the other softly-textured RPGs in the PS2 library, thanks to a lack of texture detail. Cel-shading would've been nice, but its performance in RPGs has been fairly hit-or-miss on PS2, i gather. There's all kinds to tricks to make these games look good on current consoles. Especially the kind that dictates that gameplay models should be separate from the cinema models, so that you can show more detailed characters during cutscenes; you just gotta make sure you never let the camera get too close to the gameplay models so you don't highlight what they lack. Metroid Prime and RE4 are "guilty" of this, but gameplay visuals stack up favorably, eh? Especially considering Capcom decided to use DVD-FMV's for PS2's RE4 instead of real-time imagery.
BUT THE BIGGEST TRICK HERE ARE THE *small screenshots* which simply hide the truth. Any little screen can look good, cuz all it does is SIT THERE. When you think a screen looks "good", it's time consider what the system has to "sacrifice" to pull it off.