i can't comment on the pre-COIE stuff. i've read a little, but so sparingly i'd be talking out of ignorance (more than usual!).
wolfman, waid, cooke, morrison... all great writers, and some wonderful renditions of barry allen, but it's hard to quantify what they did against creators who worked on a barry allen solo book. i think i've read all these, but alas. so of the modern day writers who have handled him...
1. williamson. almost by default. i wouldn't rank this current volume of flash with the greats, but it IS consistently entertaining. i'm... nervous for some of the elements introduced during flash war, but we'll cross that bridge when we get there. still, i'm reading the flash monthly (bi-weekly, i guess) and not fearing what i'm about to read for the first time IN A LONG TIME, and that's a nice feeling.
2. johns. the rebirth/short-lived pre-flashpoint series gets second place because it was, at worst, readable, and therefore leagues above whatever the hell they tried to pass off on us in the new 52 era. i was against bringing barry back, but you can't fight city hall, and it is what it is. rebirth and the first arc was OK, then it basically became a prelude for flashpoint. nothing fantastic, but again, i didn't want to burn it with fire, and apparently that's good enough for the silver on this podium.
3. manapul/buccellato. i thought long and hard about this, but if forced to choose i would begrudgingly re-read the manapul/buccellato new 52 run over venditti/jensen. the reason is almost entirely art-based, as manapul's flash is, of course, very pretty to look at. but make no mistake: this was awful. really, really awful.
4. venditti/jensen. take all the charm you get from a fantastic artist like manapul and replace it with brett booth, and you get garbage. straight up garbage. the story went nowhere -- the writing may have been a bit more structured than the previous duo, but my god, the art. i wouldn't wish brett booth on anyone. this was a travesty. the flash was ALL about tragedy in this short-lived nut punch of a run, and i'm not talking about the characters in the book.