I've owned a Gen3 before, and I traded it away earlier this year to get my dream wheel-gun (a decision I don't regret at all).
I disagree that the Gen3 feels better. I felt the grip circumference was too long and it the sides of the grip were too smooth. I had a Pachmayr grip sleeve on mine to give it enough tackiness.
The Gen4s recoil spring and extractor issues are all sorted at this point. I want a Glock because of (relatively) inexpensive, readily available high-cap magazines and accessories. Factory Glock magazines are ~$20 each and good quality Korean copies are ~$10 each. I can get a threaded G17 barrel for $125. Triggers and sights up the wazoo. But stock, it's an absurdly reliable soft-shooting handgun with a good enough trigger.
The only guns I cross-shopped were the M&P 9 (really nice handgun, stock trigger isn't as good as the Glocks) and the Walther PPQ (amazing stock trigger, sky-high magazine prices).
Glock didn't perfect the striker fired polymer handgun, but they're like the Honda Accord of the market. There are other models that beat it in certain categories but no one offers a better all-around package.
To each his own. I can't stand the grip of the gen4's. It seems like a pretty polarizing thing to people on either side.
I thought the M&P trigger felt better than the Glock. Maybe not as good a feel for the break or something like that, but Glock triggers usually feel really gritty ('mushy' might even be a word I would use) to me, and it's my biggest dislike in a trigger mech. Though like I said, some feel great. I don't know if it's based on model, date of manufacture, or is just altogether more random.
I will not disagree on it being a good gun with lots of parts, though. They just seem disproportionately popular compared to other polymer striker-fired handguns, so I like to pose the 'what else did you try' question. You know what you want, though; I was thinking you were one of the novice shooters looking for a first handgun.
shorty - the thing about the cheaper guns, to me, is their tendency to be a little more finicky and, eh, need a little love. Whereas some of us will clean and lube the crap out of a new gun and have no issues, or be able to rectify issues with a little bit of work (things like minor filing and polishing), a novice shooter should probably have something dead-nuts reliable. Not just to save aggravation, but because they might not deal with failures to eject or feed as well. And they're not going to do things like, say, scrutinize spent brass to evaluate the gun's performance.
Not to generalize too much, though. If someone is willing to read and use common sense, the cheaper stuff like Ruger or Taurus will work just fine.