My conclusion is that it really depends on the game, but players generally want higher-statted PCs, which makes sense because who wants to play a nobody?
Now with the older (I'm thinking B/X) having less than optimal stats weren't a big deal and the difference between a low stat and a high stat wasn't worth getting too worked up over. Of course it felt like there was some stat-creep in later editions and even that made sense to me. With all of this different classes coming out that had specific high(er) stat requirements. It seemed to me that the straight 3d6 (in order) soon moved to a straight 4d6 (drop the lowest) to 4d6 (drop the lowest) arrange as you want. I'm not going to look it up, but I also recall AD&D having alternate rolling methodologies (in the DMG perhaps) to help possibly get players the types of PCs they wanted.
When I migrated to HackMaster (4th Edition) stats went back to straight 3d6, but there was an additional fractional added (so a 3d6 + 1d100%) and you could buy fractional rolls with building points. Of course there was a cost that you maybe didn't want to pay, but it could help you get into that PC class you wanted. Knowing that as you leveled you'd get some fractional increases helped as well and there were some odd circumstances that could build you up as well. For example I really lucked out with my Double Specialist Invoker in that my school results gave me a +3 Intelligence, so I was rocking a 21 Intelligence.
Actually having a PC much, much smarter than me wasn't all it was cracked up to be as I couldn't actually access that intelligence as much as you'd think. Have to answer a riddle? Eff me man, I can't figure it out, but my PC is likely the smartest dude on the continent, if not the planet....he should be able to figure it out.
With the newer version of HackMaster gives you options, but you pay for them: straight 3d6 +1d100% gets you a nice bump in Building Points, swap two stats of the "straight 3d6" for only a 25 Build Point bonus, or just arrange the "straight 3d6" as you like for no Build Points. It also has a rule about if two of your stats are 5 or less or none above 13 you can start over (Shopkeep Rule) otherwise any other valid set of rolls have to be played/used for one session before retiring the PC from play.
For one of my PCs I had just about a set of Gawd-rolls. That kind of sucked actually. I do not remember what the straight 3d6 rolls were, but with the options given I could have conceivably chosen any race/class I wanted. The rolls were good enough that if not for the fact that two other GMs actually witnessed the rolls, I don't think I'd have been allowed to play that PC at someone else's table for fear of being suspected of cheating. The part that sucked about the rolls is that I just had too many options. This was pretty much a once-in-a-lifetime opportunity and I had a bit of decision paralysis about it. Ultimately I didn't make that choice myself. Instead I queried the group as to what they think we needed most, which was a tank. I ended up making the tankiest tank I could: Dwarven Fighter.
I haven't gotten to play this PC in years (kind of sad about it because I had a helluva lot of fun playing this PC, and not because of his ability scores!) but his current stats (mind you he gets some % bumps when leveling) at 9th level are off to the side.
His CON has a +4 bump from race that is offset by -2 bumps to Looks and Charisma.
Now I'm not bragging about this PC or anything, just I think that there's a lot of range on what can be rolled, methodology-wise and there really isn't a good reason to hate on any particular method. I think the options given are usually there to make playing a PC one wants to play, viable. The simple straight 3d6 worked great when it didn't really matter too much.
Hell, lately...especially at a convention, I've just been rolling some d30's to quick generate stats based on the d30 DM Companion. I think the method used doesn't matter unless it results in too-high of a power level than what the players & GM want to see.
