Google Sheets

Google sheets is Google's web based answer to Microsoft's Excel.  Sheets offers a good alternative to Excel, at a basic level.  What do I mean by a good alternative?

Financially

Sheets is free to personal users.

Flexibility

Sheets is web based, so it's available from any desktop or mobile device.

Ease

You need a gmail account to access Sheets and that's it.

What do I mean by basic?

Sheets features most of the common tools of Excel such as Charts, Forms, Images, Drawings and have a variety of functions that can be used to manipulate and calculate data.  Some of the features available in Excel that are not available in Sheets are:  Data connections, tables, and many advance features of data manipulations.  Sheets does offer support to import a variety of different file types, including Excel.

Microsoft has a web page that does a good job of visually showing the differences between the two apps.  Bottom line, it's really up to what you need, I think they both offer something to a variety of consumers.