I'll say this much: If the writers don't acknowledge the game, It'll be a sore point for me. Probably not a deal breaker, but definitely a sore point.
SPOILERS FOR THOSE WHO HAVEN'T PLAYED THE GAME:
Now, I am not saying that we need to hear "Oh, like that one time we fought Shandor!" or anything super specific where people will be like "WTF, when did this happen?!" But, there are certain things that don't require expositionary set up that should be included to show that the people behind the film did their preparation. The game is most definitely within the continuity of the films (they seriously almost called it "Ghostbusters 3" at one point in the game's development), and it'd be a shame to see it ignored.
I'm talking about things like:
-Slimer being kept in a containment tank next to Janine's desk. It's nice happy medium between just floating around the firehouse and how he was their mascot in RGB. I can totally envision the new GBs gathering around the tank to look at him and someone taps on it, only to have Janine startle them by coming up behind them and telling them that she wouldn't do that, unless they wanted to see what happened to the last person to tease him.
-The equipment upgrades. It's not hard at all to imagine (for people who haven't played the game and are only going off the films) that in the 10+ year period since GB2 that some upgrades have been made. Now, obviously it's up to filmakers how often the various settings for the pack established in the game are used (I have to say though, the rapid fire meson collider would look BAD ASS on screen), but they need to at least have the basic pack be a combo proton thrower/ slime blower. People will recognize that it's simply a more feasible all purpose mix of the team's 2 main packs. The only way I could forgive them not employing the game versions of the packs would be if the new team saw them and were like "OH JEEZ, SWEET HEAVY ARTILLERY!", but the team said they weren't quite ready for those yet and made them start out with the original basic version of the pack. Even still, we would see the packs as they are in the game making an appearance and the newbies would eventually work their way up to them. Also, the venting effect would be sweet on screen.
The traps. In the game, they were wireless and had various modifications to the draw down rate. Not too worried about anything except the wireless aspect though.
The PKE Meter. Honestly, a HUGE improvement over the original design, and very doable in a film.
The Containment Unit. We know it blew up in part 1. We didn't see it in part 2. In the game, we see a slighlty bigger revised edition that looks sick. PLEASE don't backstep on the Containment Unit in the new film. Seriously, there is no need to. All the equipment upgrade can be attributed to Egon and Ray's constant tinkering.
Also, the idea of "slamming" ghosts to weaken them. I thought that was a REALLY cool aspect of bustig a ghost that makes for a much more action packed busting scene than simply standing there and shooting.
-The Ecto. As established in the game, Ray at some point probably said "You know what, we don't even USE half the crap up here!" in regards to the Ecto 1-A in GB2. He retooled it again, resulting in the Ecto 1-B, which is how the car appears in the game. For the most part, it has reverted back to it's appearance in GB1, although it has kept the sattelite dish and warning stripes of the 1A. The biggest addition is the new "super slammer" trap that has been added to the roof. I personally think it's a great idea. It makes sense to have something like that, which can function as both a high density trap and a temporary containment unit of sorts which they could empty their single portable traps into without having to truck it all the way back to the firehouse. We need at least Ecto 1-B...if not 1-C.
As a bonus, it'd be cool to see the Ecto-8 boat from the game somewhere in the background.