SEGA's Virtua Tennis 3 could be the most accurate console-to-PSP port that seen so far. In fact, if you were to play it alongside the PS3 version (which IGN have in-house and previewed last week), it would be difficult to tell the difference between the two. Impossible as that may sound, it's because of the PlayStation Portable's small LCD screen -- it keeps the resolution and detail discrepancies from being immediately noticeable (they are there; they're just hard to spot.)
But when IGN say that Virtua Tennis 3 is an accurate port, it isn't in reference to the visuals. No, what it really means is that the game's PSP content is identical across the board. In fact, some could say that the handheld version is actually bigger than its PS3 counterpart because it allows people on four different machines to play each other (via ad hoc). Without an online feature, you can't do that on Sony's next-gen system.