What is the best alternative to Street View - street view maps on iPhone?

Google Earth, A tier, #2 in street view.

Is there a free alternative to Street View - street view maps?

Yes: Google Earth (A tier, #2) is free, with no in-app purchases.

No. Street View - street view maps is #1 in street view.

Street View - street view maps is S tier, #1 of 7 in street view. Here is everything that competes with it on iPhone, in tier order.

2
Google EarthA
Free · ★ 4.0 · 47,490 ratings · score 88
Google Earth is a mapping app for viewing satellite imagery, 3D terrain and buildings, and Street View, and for…
3
MAPAS: Live Street View & GPSA
Free + IAP · ★ 4.3 · 4,672 ratings · score 87
Free navigation app for browsing street-level imagery, live cameras, 3D and satellite maps, and basic GPS tools.
4
GStreet - Street Map ViewerC
Free + IAP · ★ 4.5 · 13,604 ratings · score 65
Views street-level panoramas on a map, with address search, navigation, bookmarks, and traffic and cam options in.
5
We Camera 03 | Street View AppD
Free + IAP · ★ 4.1 · 5,121 ratings · score 59
Street View and map viewer with current location navigation, pins, routes, four map types, sharing, search and traffic.
6
Live Satellite View & GPS MapsD
Free · ★ 4.3 · 2,800 ratings · score 57
Free Navigation app listing satellite imagery of any location on Earth, with GPS tracking, map layers and offline.
7
3D World Map VRF
Free + IAP · ★ 4.5 · 7,386 ratings · score 43
Street view and 2D/3D world map app with VR 360° panoramic tours and VR live video, per its App Store description.

What is the best alternative to Street View - street view maps on iPhone?: Google Earth, A tier, #2 in street view.
Is there a free alternative to Street View - street view maps?: Yes: Google Earth (A tier, #2) is free, with no in-app purchases.
Does anything rank above Street View - street view maps?: No. Street View - street view maps is #1 in street view.