The best replacement for ios4 is ios3.

The best alternatives to ios4 are rated as following:
★★★★★  ios3
★  ios5
★  froyo

Your alternative for ios4 is not listed? Suggest!
Speaking about ios4, one probably shouldn't forget about iphone 2g.

Other search terms related to ios4 and their ratings are:
★★★★★ iphone 2g
★★★ iphone 3g slow
You have in mind a companion for ios4 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of ios4 in all years. Click on graph for more.
ios4
ios3
ios5