Well, that depends on what spell the spell-like ability is mimicking. At-will Fireball, say? Yeah, that’s worth a lot. But there’s a big difference between Fireball and Ray of Frost.
Cantrips are also a significant class feature when used effectively. If you think of them less like a bonus, and more like, say, uncanny dodge in terms of efficacy, it might make more sense.
Most cantrips pale in utility after a few levels. A few, like Guidance and Light and Detect Magic, remain useful throughout a campaign.