I'm glad irdeggman threw out sleep for comparison. Comparing the two shows how truly sick entangle is, and illuminates some of the thinking of the desing team. Sleep renders targets helpless, so it needs to be reined in, while a spell that "merely" immobilizes and entangles targets can be given all kinds of advantages in terms of area, resistability, secondary effects you have to endure even if you save successfully, etc.
A sorcerer who picks up sleep would be looking to swap it out ASAP. Its scalability is pretty sorry. OTOH, entangle will always be wonderful. Strength checks aren't level-impacted, and the Escape Artist check is high enough to be a challenge to even characters with double-digit levels (few targets have Escape Artist ranks in the first place, so it's not really that level-impacted either).
Spell resistance doesn't help, immunities against entanglement are uncommon at best (flight is the most obvious "immunity", but most creatures are earthbound even at higher levels). Really, it's a 1st-level spell to hang on to.
As to comparing entangle to magic missile, I think a spell that inflicts a relatively low amount of damage against a single target (or outright pitiful damage against mulitple targets) is not as useful as a spell that devastates the formation of large groups opponents.