Aries and Gemini surely have many things in common. Both share a love of movement and new horizons, both thrive in an active, dynamic environment. But the minds of Gemini and Aries function differently. Aries can't see why gemini keep wasting energy communicating for the bare sake of communication, (energy should be wasted in the Aries-way) and have trouble respecting the constant change of opinion and believing in the authenticity of the whims and stream of consciousness-ideas that flow through Gemini. Additionally, Aries may consider Gemini to lack honestness and passion, regarding their logic and impersonal stance as cold or too detached.
Gemini on the other hand likes the passion and enthusiasm of Aries but cannot help but become annoyed by their somewhat one-sided world view and their personal pride. Sometimes pompous and smugly self-celebrating, the Arian ego can drive the airy sarcasm of Gemini a bit insane. And perhaps Gemini is tempted to constanly mock and verbally challenge the Aries. Very fine friendships can come out of this interaction, as the dialectic is excellent and the instinctive sympathy is mutual. Romantically it's more challenging; even though both signs are attentive lovers, their view of love and partnership is usually found at different levels. Both love independence, but the Gemini's considerable social needs could be seen as lack of commitment and partnership-focus by the Aries partner. Could certainly work though.