Electric: Oh my, so many options... Obviously Pachirisu (IS there anything else you'd want to start with? :/)
Dark: It's probably Absol at this point, because Disable is now blockable with Unown G. Sure, your opponent can draw cards back if they get Claydol out. Absol's no longer "Oh, my opponent doesn't have a hand, neener neener neener~~". Heck, it NEVER should be played like that. Absol's point is to remove tricks like Rare Candy and Scramble so your opponent can't use them later, and that purpose still exists.
Water: Lapras. 80 HP and Castaway for one water? I'm sold.
Colorless: I'd have to say Stantler here, actually. Sentret's frankly not all that great on it's own, while Stantler can get you any supporter (and thus anything rather quickly, unlike Sentret who's Pokedexing until you find a Furret), and can auto-confuse basics (like Absol and starters)
Fire: Um. There really isn't a whole lot impressive here. For pokemon who's attacks are most impressive while basic, I'd have to say Charmander. 2 Fire for 20 and spreading 10 to bench ON A BASIC isn't too bad. Heck, Charizard can make that 70 damage and 10 to bench (but you'll eat Memory Berrys at an insane rate). Entei wouldn't be too bad, except it can't do anything at all until it gets 3 energy *sigh*.
Fighting: Baltoy's pretty dang awesome. Psychic Balance for colorless energy? On a pokemon that evolves into permenent Birch? Sure, why not?
Psychic: Ascension Shuppet is one of the few old cards to be good, and for great reason; such early evolution into such a nice early game attacker is brilliant.
Metal: It'd have to be Skarmory. Discarding Energies isn't half bad, though it's energy cost is downright terrible. Please let DP5 come out with something to... You know, actually make metal types worthwhile :/ The Psychic Resistance is good on a starter though, as is it's mere 1 retreat cost.
Grass: ...*sigh*, the type that also has just about no good starter. Kricketot works great for it's own deck, but isn't for every grass deck. Caterpie is absolutely amazing (turn 1 stage 2 with 120 HP and 30 damage for 1 energy? Not to mention that attack HEALS, and the stage 2 has free retreat? OH SHI-) Not much more beyond that.