This guide is designed as a quick reference check for deck builders looking to ensure that a minion meets the vanilla test. I have tabulated some of the standard go-to cards as a comparison.
Archetypes and class specific minions (which are usually better than neutral minions) are not considered.
Cards have been selected on the basis that they provide decent stand-alone value for mana and have balanced a attack/health. There are almost definitely better cards to be had if you building a deck for a specific purpose but this table is meant as a simple go-to comparison not for detailed better/worse analysis. Arena minions would be weighted slightly more defensively (ie 2/3 and 3/4 instead of 3/2 and 4/3), to prevent them from being traded with a cheaper minion.

* Legendary cards are included only as the exception, not as standard.

Standard Table

Cost Basic Classic Blackrock
Mountain
Grand
Tournament
League of
Explorers
Whispers of the
Old Gods
Other Mentions
0   Wisp - - Murlock Tinyfin - -
1 Voodoo Doctor Abusive Sergeant - Injured Kvaldir - Tentacle of N'Zoth  
2 Bloodfen Raptor Faerie Dragon - Boneguard Lieutenant Huge Toad Beckoner of Evil  
3 Shattered Sun Cleric Harvest Golem - Light's Champion - Twilight Elder  
4 Chillwind Yeti Dark Iron Dwarf - Evil Heckler Tomb Spider C'thun's Chosen -
5 Frostwolf Warlord Silver Hand Knight - Clockwork Knight Naga Sea Witch Corrupted Healbot Azure Drake
6 Boulderfist Ogre - Drakonoid Crusher Master Jouster Wobbling Runts Skeram Cultist Emperor Thaurisson
7 War Golem Ravenhold Assassin - Captured Jormungar - - -
8+ None Any Giant (8/8) - Frost Giant Fossilized Devilsaur Blood of the Ancient One  

Wild Mode Table

Cost Naxxramas Goblins Vs
Gnomes
Other Mentions
0 - Target Dummy -
1 Zombie Chow Clockwork Goblin -
2 Haunted Creeper Micro Machine -
3 Shade of Naxxramas Spider Tank -
4 - Lost Tallstrider Piloted Shredder
5 Sludge Belcher Salty Dog Ancient Healbot
6 Piloted Skygolem Drakonoid Crusher -
7 - Dr. Boom -
8+ - Force-Tank MAX -