Maybe Im biased but I say buy the tools a bunch of tjets, put on ur jammis and start tuning till your nose bleeds..

Nah serious though, if you think the newer G+ is your thing buy 1 or 2 and try um. or maybe Tyco cars like suggested. It finding what you like. But your old pancake cars with a little tuning would probably wake right up. Id start with a bag of new brushes and a few sets of shoes. Clean um up reoil them. maybe get a comm tool and clean up the commutators and flatten them.
I think your feeling the frustration of haveing old track that has sat and old cars that sat that all need attention. Pick a car and go 100% through it. And clean your track REALLY good. How I did my old MM track was to wash it in windex and clean the slots out when I got it out, then once all dry I made a few passes on the rails with a 320 drywall sponge, then Mr, Clean magic eraser, then wipe it down with eather swiffer wipes or and old T shirt and blow out the slots.
You'd be surprised how much the rails will shine up with a drywall sponge, they may look clean but you'll see an Imediate differance in shine.
An example, I have a 4lane bull ring I just recently build all clean and nice and tweaked etc... My cars run so good on it. I have another track I have not touched since July its sat in the dusty basement, when I recently(few days ago) re set it up my tuned cars were stopping all over and blowing orange sparks off the shoes. I have a whole reclean to do to make um run.
I suggest you take ONE car and tune it real good,Lightly sand the contact patches of the shoes on like 2000 grit paper, and make sure they are flat to the rails, clean out all the old oil, clean the commutator(I really suggest the vrp comm tool)put new brushes and then just drive it and have fun, get the blood pumpin and the rest of the cars will come alonmg as they do, when they do.
Actually if the cars arent too bad, you may just need clean the old oil out and reoil, then prop up the rear wheels and run them a few minutes to get um loosened up again.