Wube (creators of Factorio) have the best customer policy in game development.

• Don’t go on sale so you will always pay the cheapest price.
• if you have the game on steam you can download a DRM-free version directly from their website. (alongside all old versions)
• Encourage the community to create mods, host your own mod portal accessible inside the game.
• Make a good game.
• Be open about game development through monthly blog posts.

The only way I would like it more is if the game was open source but since that’s impossible to sell I will take this.