The best replacement for gmail app is mailbox.

The best alternatives to gmail app are rated as following:
★★★★★  mailbox
★★★★  mail
★★★★  ipad mail
★★★  ios 7 mail
★★  sparrow
★★  mail app
★  sparrow ios
★  htc mail
★  apple mail
★  imailg
★  iphone mail
  iphone mail app
  ios mail

Your alternative for gmail app is not listed? Suggest!
Speaking about gmail app, one probably shouldn't forget about multiple accounts.

Other search terms related to gmail app and their ratings are:
★★★★★ multiple accounts
You have in mind a companion for gmail app and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gmail app in all years. Click on graph for more.
gmail app
mailbox
mail