Based on feeling:
* Dreary is to happiness as a cloudy day is to sunshine. (Contrasting with a positive opposite)
* Dreary is to exciting as a monotone voice is to a vibrant one. (Focus on lack of energy and excitement)
* Dreary is to inspiring as a stagnant pond is to a flowing river. (Focus on lack of movement and vitality)
Based on visual imagery:
* Dreary is to vibrant as a faded photograph is to a colorful one. (Focus on lack of brightness and color)
* Dreary is to lively as a deserted street is to a bustling marketplace. (Focus on lack of activity and life)
* Dreary is to beautiful as a dull gray sky is to a bright blue one. (Focus on lack of aesthetic appeal)
Based on sound:
* Dreary is to cheerful as a sigh is to laughter. (Focus on the emotional tone)
* Dreary is to lively as a dripping faucet is to a lively melody. (Focus on the lack of rhythm and pleasantness)
* Dreary is to uplifting as a mournful dirge is to a joyous fanfare. (Focus on the tone and mood)
The best analogy for you will depend on the specific context and the aspect of "dreary" you want to emphasize.