Despite this game's age, I still find it endlessly fascinating and enjoyable. I especially enjoy the game editor that Blizzard packaged with SC. You can always wish it had this or that extra feature, but it is remarkably capable and I have used it to build several maps.
As to the maps themselves ... I prefer cooperative maps; that is, me and a friend pitted against one or more AI opponents. My buddy Joe and I have spent countless hours gunning down hordes of Zerg, and there is no difficulty about which of us is the better player. (Actually, I can't beat him one-on-one anyway.)
One major flaw with the stock AI is its inability to lay down an effective defense. To conpensate for this, most of my maps start with heavily fortified enemy areas, while you have to build yours up from scratch. This helps make the games more competitive.
Another challenge for you is that you are often on a time limit. You get 90 game minutes (or 60 clock minutes if you play at the fastest speed) to take out all the enemy buildings. We have lost more than one game by running out of time with one enemy building stuck somewhere off in a corner that we never found.
Finally, the maps are set up with the two humans playing Terran, and often you don't get to build Battle Cruisers. There isn't much that can stand up to a squadron of BCs, so removing them makes the game more interesting.
Dark Night Two humans against two Terran AI opponents. Ninety minute (game-time) limit. This map contains four rescuable BCs for each human player. Once you get an SCV to your four BCs, they are under your command; you just can't build any more, so keep them repaired. Note: Rename this map to (4) DarkNight.scx.
Crossroads Two humans against two Protoss AI opponents. Ninety minute (game-time) limit. No BCs available. This one took Joe and me a long time to beat. Note: Rename this map to (4) CrossroadsA_TvP.scx.
River Crossing Insane
This
is the standard River Crossing map, but the opponent AI kicks into
Insane
five minutes into the game. Makes for an interesting
solitaire game.
Note: Rename this map to (2) River Crossing AI.scm.
Water World
A human team versus an AI team, up to four players on each
side. All bases are islands, so ramping up your defenses
quickly is paramount. Then you have to expand your bases
because the starting areas don't have enough resources to carry
you. Very challenging map. Note: Rename this map to
(8)WaterWorld.scx