General advice for maximizing fun playing multiple games of Dominion
We've used a mixture of user-selected and randomly selected cards. One scheme that's worked: each player gets to pick one card they don't want in the next game (this is done first), and then two cards they do want in the deck. The remaining 2 cards are selected at random. (This was for a 4-player game; in a two-player game I'd experiment with 1 or 2 banned cards and 2 or 3 selected cards).

The purpose of this method is to give each player the ability to tailor the deck to include a couple of kingdom cards they think might be synergistic, enabling them to try out a new strategy. Also, as the latter players select their cards they're able to try out counters and other means of blocking what they think the other player's strategies might be. 

Once you become experienced and comfortable with the cards and the potential interactions this method turns into a meta-game that may detract from the fun, but early on, while you're still learning the ins-and-outs of a new set of cards, it's an easy way to design decks to test out specific theories--and the random cards that are still in each game provide a mechanism for random learning and discovery.