Haunter/Dusknoir: A bit dark, and what's with the glowy bit, but OK.
Donphan/Rhyhorn: Not very different to a regular Donphan really, try using more Rhyhorn parts.
Is that a Heatran prevo? If so you have some good scratching ability, it just needs touching up - the lines for example are a bit jagged and also quite thick in places, apart from that, excellent.
Torterra/Venasaur: A bit C+Pish, try scratching parts a bit more.
Registeel/Voltorb: relly good, but the eye on the shoulder thing looks a bit wierd.
Entei/Moltres: Good, but the only thing you've brought across is the wings and they're a bit out of proportion ie: you could scratch them a bit bigger to make 'em look like they could actually carry it.
Verdict: Yeah, you are good at spriting, keep up the good work .