I played a lot of SC1 but didn't really follow the eSports scene at that point. What is wrong with Blizzard maps that other map makers do so much better? I've played some ICCup maps and like them but didn't see what made them so much better.
There isn't a 'worse' or 'better' really, but there are definitely some maps that cause very tricky situations for specific matchups. Jungle Basin for instance is very tough ZvT, since middle-late game there isn't a comfortable third expansion for zerg and the constricted middle area makes it technically difficult to pressure without already having a significant advantage. There are some other unnecessary differences too- Scrap Station has one ramp farther away than the other, meaning you'll need an extra creep tumor to reach the bottom.
iCCup maps are usually very well taken since they're mostly (if not all) copies of SC1 maps that have had decades of fine-tuning to balance, something none of the Blizzard maps have had (sans LT.)
I'd really like to see some bigger 1v1 maps or more open (I love XelNaga Caverns) that allow for positional play (and a counter-based unit macro play), but that's just because I play a reflexive Zerg. Generally Blizzard has done a pretty good job; with the exception of Delta Quadrant and Jungle Basin I'll play any of the maps without any real complaint.