I think the success of this game is going to be short-lived. Or rather, the game will remain successful with urban players and those lucky enough to live near dense clusters of Poke Stops, but disadvantaged players will quit playing in large numbers as they realize what a pain-in-the-ass the game is for those living in rural or suburban areas (or on the wrong side of town).
The game is grindy as fuck, and you needs hundreds (later thousands) of Poke Balls to advance. And that grinding is really very boring. It's pretty much: Catch as many Pidgeys, Weedles, and Caterpies as possible (these are the easiest Pokemon to evolve), pop a Lucky Egg (double XP; see
this chart to plan), evolve those Pokemon. Rinse, repeat. Rare Pokemon? Pfft. Same XP as common, but much harder to catch and evolve.
That said, the grindy aspect is somewhat forgivable because it's probably meant to prevent those who play all the time (or spend a lot of money) from completely roflstomping people who have lives outside the game. Still, grinding shouldn't have to be so damn boring. How about more XP for catching rare or higher-CP Pokemon? How about a greater variety of Pokemon instead of the same 20-30 or so repeated ad nauseam?
Grinding aside, the biggest help for me would be the ability to suggest Poke Stops. There's a park near my apartment with a memorial, a small bandstand, and two pavilions. The memorial is a Poke Stop, and I spin it on my daily walk, but that's not enough to sustain more play than the walk itself per day. If I could mark the bandstand and pavilions as Poke Stops, that'd be enough for people in my neighborhood to actually play a decent amount each day. I've seen clusters of three and five Poke Stops clumped together a couple towns over, so four in a small park shouldn't be a problem.
That said, there should probably be a restriction to limit abuse and keep the number of suggestions manageable. Perhaps each player could get one suggestion at Lv10, Lv20, and Lv30?
Another option would be to have Poke Stops give a number of items based on how far away the nearest Poke Stop is located. Maybe three extra items per kilometer to the next Stop? So if the next Stop is two kilometers away, that Stop would give six extra items per spin. That's still not much at middle and later levels, but it'd be a significant step towards leveling the playing field.
For now, I can drive to a park on the other side of town that has four Poke Stops and two Gyms, but taking a 15 minute drive (30 minutes round trip) just to take my daily walk in an area with multiple Stops is wearing thin. I think the game might have been better off with Poke Stops at every intersection so that you could hit multiple Stops by walking around the block regardless of where you happen to be located. Parks, churches, and whatnot could have all been Gyms and higher-chance spawn areas.