A great DLC should build on an already great game. It should provide a new area of exploration, new guns, new dialogue, etc, with a price that should be judged based on the size and length of it.
It should, however, not be an easy way out for developers who create a questionable or straight up bad game, only to then sell you additional content that provides the experience you originally asked and paid for.
That's like ordering a meal and receiving an empty plate, only for the restaurant to condescendingly apologise, and then give you what you want... if you pay a little extra. The anger might dissipate, but it's doubtful you'll ever be going back.
That said, not all DLC is tantamount to the digital antichrist, and in fact, some are a breath of fresh air in a game environment you might have otherwise depleted.
Consider these the 10 great DLCs money can buy, adding to their respective creations and - in some cases - being even more enjoyable overall.
10. Dragonborn - Skyrim
By this point, Bethesda were well revered for releasing high-quality DLCs, but there is a good portion of people who find the Skyrim DLCs to be quite lacklustre.
The player's main quest revolved around a new adversary who threatens Solstheim and the player's existence - the first Dragonborn: Miraak.
Going for around £10, this DLC allowed longtime fans to return to Solstheim from Morrowind in a journey containing new towns, dungeons and quests for the player to encounter, all in a bid to become more powerful thanks to shouts that can tame the dragons themselves.