I think as long as the original actors are available, and considering the medium, it'd be ridiculous to not use them. I'd love to see Akroyd, Murra and Ramis in London and/or Prague, though.
Yeah, sure: their voices are still the same, it's not like trying to make a live-action sequel, where all the actors are visibly advanced in years. Voiceacting's great. Hell, isn't Michael J. Fox still doing voice work, even though Parkinsons prevents him from appearing onscreen?Great idea.
But I think the insurmountable problems are going to be finances and ego (not "Egon"). You've got these guys that have all got their own amazing careers, are working and making plenty of money with their current pursuits. The amount of money it would take to lure them to the voicework for a videogame would probably make any ROI report burst into flames. "Why are we paying Bill Murray US$1m for 3 days of recording and 1 day of pickups?" And this leaves aside personal issues any of them might have in working with the others again. Isn't Bill Murray kind of famous for being a pill? Is Ramis even interested in doing anything with the character anymore?
Dollars to donuts, the next Ghostbusters project will tie into the old animated series, or even be co-dev'd alongside a new animated series.